This article is a travel topic
Virtually all travellers will need to spend money on their trips. There are a number of ways to do this. You are always trading off expense, risk and convenience.
Automatic teller machines
Automatic teller machines (ATMs) are, overall, probably the most convenient way of obtaining cash worldwide. All you need do is memorize your Personal Identification Number (PIN) code and carry around your ATM card. The biggest disadvantage of using ATM's is the fees involved. In addition to the fees that your bank charges you for the withdrawal, they will probably charge you an additional "Network Fee" for using the Cirrus, or Plus networks, and the bank that owns the ATM often charges "convenience fees" for using their ATM. The "White Label" ATM's (ATM's not associated with a bank, usually located in convenience stores and hotels) often charge even higher convenience fees. These fees are almost always fixed amounts, so it is usually better to do fewer withdrawals that are large amounts rather than a number of small withdrawals. Your bank also usually gives you a better currency exchange than you could get elsewhere. If you withdraw small amounts it is not uncommon to pay as much as 5-10% in fees.
There are two major international ATM networks, namely Cirrus (affiliated with MasterCard) and Plus (affiliated with Visa). Nearly all international-enabled ATMs support both and nearly all bank cards can use both, although you may want to confirm with your bank — in particular, you may have to get international ATM support specifically activated for your bank account.
There are some catches to beware of:
The acceptance of credit cards varies by country. Rarely can you buy everything by credit card, but in most of the developed world you will be able to buy most of your major purchases (hotels, air travel, car rentals, expensive purchases and expensive restaurant meals) on credit card. In less developed locations your credit card may be totally useless. In all cases there will be some expenses that cannot go on a credit card so you cannot rely on a credit card exclusively.
The biggest advantage of a credit card is convenience. You do not need to know exactly how much money to bring with you. You also don't need to deal with the inconvenience of money exchange.
The next biggest advantage is the low risk. In most countries you are not responsible for any expenses made on your credit card that occur after you report it lost or stolen. Credit card companies will also protect you if you are charged more than you agreed to pay, or if you pay for something and never receive it. However, be careful where you use your card in some countries, as your card can be cloned (duplicated) without your knowledge and then used for fraud without being physically stolen.
Many credit cards also include some forms of insurance protection for all expenses made with the card. This can include cancellation insurance for flights (usually only in the case of serious sickness), theft or loss insurance for goods, Collision insurance for rental cars and even travel health insurance when you are travelling. You should look over you credit cards insurance carefully before you start to travel to see what it provides. It may even be worth getting a travel credit card, if you don't have one, just for these coverages. Also note that you can often tie in a credit card to a frequent flyer program, so you get more miles and free trips faster.
The biggest disadvantage is cost. At one time credit card companies used to apply the exchange rate they got to your exchanges. However, most credit card companies now incorporate a exchange fee into the exchange rate that they offer. This is generally in the 2-3% range, though a few such as Capital One charge nothing. You can call your credit card company and ask what the fee is as well as asking what the current exchange rate is for the currency that you would like to find out about. One thing that should be noted is that the exchange rate is applied at the date the expense was posted to the account, not the date the charge was made. Therefore if you are dealing with a fluctuating currency it is impossible to know exactly what exchange rate will be applied for an expense until a few days after you make the expense. Hotels in some countries (notably Ireland) will perform the currency exchange at the time of the transaction. This removes the uncertainty about what you will pay, but the downside is that the exchange rate fee (about 2-3%) that is incorporated into the transaction may well mean that this is not in your favor.
If you have multiple credit cards it is often a good idea to only carry around the one you will usually be using and keep others in a safe location. Then if your main one gets lost or stolen you will not be left without a credit card, or have to go through the hassle of replacing a credit card in a foreign country.
Banks in some countries will stop your card if they notice unusual activity such as sudden transactions in a foreign country. So, it is best to notify the bank beforehand and get a note added to your account so it does not get passed through their fraud section.
Note that withdrawing cash from ATMs using a credit card will often count as a cash advance with your bank, causing you to pay higher interest. There's no point saving 2%, only to pay 19.9% interest on the money you withdraw!
Travellers' cheques were at one time the primary method of taking money with you when you travelled. These days they are not as common, but they are still widely available and relatively widely accepted. Generally these are not accepted as widely as credit cards and they are usually not as convenient to use. In general, only the largest stores and hotels will accept cheques for payment as is.
Travellers' cheques are issued in a specific currency. The American Dollar is the most common currency, but many different currencies are available. American Express credit card holders can get emergency cash in the form of its travellers' cheques at foreign American Express offices, and designated affiliates (often a travel agency or bank). If the location is not a bank, you will have to go to one or a foreign money exchange to cash the cheques. Be sure to bring a blank cheque from your checking account back home or at least know the account number. There is a one percent fee for issuing the travellers' cheques, and the total sum is NOT a cash advance on your American Express card. (They will cash advance your credit card without further permission from you if there's a delay in cashing the check, though. Keep tabs on your checking account, and make sure it clears in a few days.) Also, there's no requirement that you're destitute, as the service is available for whatever reason.
The main advantage of travellers' cheques is complete protection against loss or theft. Once you report them as missing, the issuing company will replace them. However, you must also keep a record of your unused cheque numbers, and the replacement process can take time and be inconvenient.
With travellers' cheques, you will typically have to pay fees both to buy them and to cash or use them. This may be a straight fee, or it may be hidden in the exchange rate if you are buying them in a foreign currency. If you are buying them in a foreign currency, it may be worth it to find out if you can buy them with cash in that foreign currency (assuming you have some already).
When cashing your checks, pay close attention to commissions and fees: if the fee is per cheque, cashing many small checks can be very uneconomic. Be suspicious of claims of "no fees", as this usually means that the exchange rate is terrible.
Do not expect your home debit card to work in foreign countries. However, if you have a debit card that is linked to one of the key networks, there will be few difficulties: - The Maestro brand (or Cirrus) usually has a red and blue Mastercard like logo on the card itself, since this is a MasterCard product. - The PLUS brand also works in the same places as a VISA credit card. To obtain cash in a foreign country look for an ATM that sports the same logo. While exchange rates are good additional exchange fees usually apply. It should be noted that in Japan, not every ATM that sports a MasterCard/Cirrus/Maestro or VISA/PLUS logo accepted foreign credit cards; since 2007, however, this has been rapidly changing and most ATMs now accept international cards, including those at post offices, 7-11 stores and Citibank.
Cash is the most versatile method there is. Virtually everywhere takes cash. The one exception is that some car rentals may not rent you a car or ask for a very large deposit if you don't have a credit card.
In some countries you may be able to get by entirely with US Dollars or another currency. However, this will often be at a huge expense as the exchange rate offered by merchants and hotels is usually not very good. Merchants in border communities may be more accepting of neighboring currencies. For example, northern border areas in the United States may accept Canadian coins on par with corresponding U.S. coins, but not Canadian dollars, and in the U.S. South a Canadian quarter is worthless.
For distant foreign travel, be sure to bring only paper notes in good condition and only the most recent redesign (unless it's really new). Banks at your destination cannot easily or cheaply exchange worn-out currency for replacement as they can with their country's own currency. Worn paper currency may be devalued if it is accepted at all. Even if in good condition, previous designs of your currency may not be accepted due to counterfeiting concerns.
This biggest disadvantage to cash is the risk. If you lose it you can't get it back, and if someone finds out you have a large wad of cash you become a potential mark. Some defenses are discussed in the pickpockets article, but there is no complete defense — carrying cash always involves a risk.
When using local money, familiarize yourself with the basic note designs and their security features (watermarks, holograms etc), and watch out for counterfeits and obsolete currencies. Banks and money changers (operating out of an office, not flashing wads of cash from a coat pocket) are nearly always safe, but taxi drivers, petty traders and such, may be tempted to palm off useless bills. When in doubt, reject unfamiliar bills, and be particularly suspicious of large notes.
Where to exchange cash
Money exchange is a very complicated business. All money exchanges work on the basis of selling a foreign currency at one rate and buying at another, with the difference being the spread. Newspapers usually will quote the average of the two as the daily rate. Where there is more competition, the rates are likely to be better.
Currency exchanges are not all created equal. Where the best rates are available varies tremendously from one country to another and from one currency to another. In some cases it may be better to exchange your money before you leave, in others it may be better to do it in your destination. Rarely is the most convenient location (such as at airports, or major hotels) the best rate available. In some cases it can be significantly higher. Regardless, make sure you know the current exchange rate before you leave home. 
As you lose some money on every currency exchange, you should not exchange more than you need. If you have a large chunk of cash left over at the end of your trip and you were planning on paying for your hotel or car rental with credit card, pay for some of it with cash to get rid of the currency. If you have foreign coins, you will probably not be able to exchange them for domestic currency when you return home, even at a dedicated currency exchange counter. Convert as many coins as you can into bills before you leave the country. If you don't want to keep the leftover coins for souvenirs, drop them in a local tip jar before leaving. At some major airports there are drop-boxes where foreign travelers can donate extra coins to charity just before they get on their departing flight.
If you are exchanging very large amounts of money it may be possible to do a certified cheque currency exchange. This is sometimes offered at a cheaper rate at currency exchange. You bring in a certified cheque to a currency exchange and they give you a certified cheque made out to you in the new currency.
Most major currencies are subject to counterfeiting these days. Study the bills of the currency of the foreign country to become familiar with how it is supposed to look and feel. Almost all currencies employ anti-counterfeiting technologies, including colour shifting ink, watermarks, special threads, iridescent inks, raised printing, holograms and other features. Become familiar with them so that you can quickly check them when you get a new bill whether it is as change or from a money exchange. If you are unsure, don't be afraid to say you would rather get a different bill, or just say you would rather get 2 smaller bills for change (As an example if you get a ten in change that you don't like the look of, ask for two fives instead). If you end up with a counterfeit you won't get compensated, and you may end up having to explain it to the police.
A convertible currency is a currency that can be easily converted into another country's currency; conversely, an inconvertible currency is theoretically worthless outside its country of origin. A few countries, like Cuba, still issue one convertible currency for tourists and one inconvertible currency for locals. In some countries like Tunisia and India, importing or exporting (inconvertible) dinars and rupees is technically a crime, although such regulations are rarely enforced for small amounts.
Convertibility is set by law and not always entirely reflected in reality: some currencies like the Indian rupee are inconvertible in theory but fairly easy to trade in practice, while others like the Swazi lilangeni are fully convertible in theory but next to impossible to sell or buy in most of the world.
Despite the name, inconvertible currencies can often be purchased at a discount outside the country of origin, as people holding onto them want to get rid of them. Finding somebody to buy them is more difficult. Also note that state-run shops in some countries will also insist that tourists produce certificates of exchange to prove that their money was obtained from a legitimate source like a local bank at the official (usually poor) exchange rate, and such certificates are also often required if you want to change back any unneeded money within the country.
If travelling to a country with an inconvertible currency or one that you can't, in practice, buy or sell in your home country, you should convert all your money to a major international currency (US dollars, Euro or the British pound, whichever you can) before leaving the country. In general, these currencies can be exchanged at banks anywhere in the world: US dollar, Euro, British pound, Japanese yen, Swiss franc, Australian dollar and Canadian dollar.
In most of the world, the only "real" money is the local currency. If you want to buy anything you will need to get some of the local money. Some businesses who deal with a large number of foreign tourists may also accept foreign money, but often at an inferior exchange rate to allow for the inconvenience.
In many poorer countries with inflationary, unstable, and/or inconvertible currencies, a foreign hard currency may prove more useful. Although its value fluctuates, the "gold standard" for currencies remains the U.S. dollar. It may be accepted as payment (though not necessarily at a great exchange rate). In fact several countries in the Caribbean, the Americas and South-East Asia use it as their de facto – or even official – currency. The euro is also increasingly well accepted, at least in regions with many European visitors, and small countries with economically powerful neighbours may also accept regional hard currencies (e.g. the Thai baht in Laos and Cambodia, the Australian dollar, or sometimes the New Zealand dollar in much of Oceania).
You can use hard currency when haggling with locals by offering hard instead of local currency. Use the conversion rate to your advantage and make an offer in hard currency. Showing a few US dollar bills in the process might help but be sure to only show what you are willing to pay.
It is wise to carry an emergency stash of hard currency separated from all your other belongings and valuables.
Black market exchange
In some countries the official exchange rate is fixed at a completely unreasonable or unrealistic rate. In these countries the black market will provide much more realistic evaluation of the currency's worth, and is practically unavoidable. For example, in 2007 the official exchange rate was 250 Zimbabwe dollars to the US dollar, while the black market rate reached 600,000 Z$ to the dollar.
That said, the risks of black market exchange are legion. First and foremost, black market exchange is illegal and both buyer and seller may face severe sanctions if caught: the seller may even be (or work with, or tip off) a police officer out to trap tourists. Second, the risk of fraud is high: you may get obsolete banknotes, fake banknotes, less than the promised amount or nothing at all. Consider carefully whether you need to exchange in the first place, as businesses in countries with basketcase currencies will often be more than happy to accept hard currency directly instead (although this, too, will often be illegal), and you may get all the local currency you need back as change.
The key guideline to successful black market transactions is to receive the money before you hand yours over. Count the bills, inspect the bills carefully, compare them to any you already have, and only then surrender your own money to the vendor. Do not allow them to take back the money they gave you, as this is where various sleight-of-hand tricks can be pulled to replace the legitimate bundle with something entirely different.
In countries where foreign exchange rates are reasonable, it is best to avoid the black market entirely: you risk losing all your money for gain of a few percent at most.
An exception may apply in countries such as Nepal and India where doing a legal exchange at a bank can involve wasting an hour or more but most hotels will change money for you instantly and fairly safely. The rate may not be much better, but the convenience is.
Getting Money Fast
If you have someone willing to send you money, there are several options for getting money fast in an emergency. These include:
Why not scan a credit card, upload it to an email account and in the case of an emergency, just go to an internet cafe and western union yourself money?
Costs depend on a number of factors, including affluence, accessibility, taxes, rent etc. It is a good idea to estimate your costs before you travel. In general, richer countries like the United States, Canada, Japan and Australia are more expensive than poorer countries like let's say Somalia, Ethiopia or East Timor. Even within countries, costs can vary. In China, rural areas tend to be cheaper than urban ones due to the relative affluence of urban people. However, in Australia, rural areas are usually more expensive as people are generally affluent nationwide and rural areas are much less accessible, making transportation, supplies, utilities, etc. expensive.
Often you have to declare if taking more than 10,000 dollars, euro, or similar amounts into or out of the county. Failure to do so may result in having the entire amount (not just the excess) seized by custom officials. Don't forget monetary instruments such as travelers checks count as well. The rules about personal and business checks can be confusing. If the check is "cashable" and payable to yourself (or traveling party, etc.) that counts against the total. But when abroad, you can mail a check to someone in your home country (or do it online) provided the bank which the check is drawn from is located in the same country. (If not, you must report.) In other words, the funds never accompanied you, and you're just giving permission to your bank back home to pay someone domestically.
Some nations (mostly third world) have such a low import/export limit in the country's home currency (not US$, euro, etc.), the export or import limits may practically represent pocket change. Often, this is due to local laws not having been updated for hyperinflation. However, in those cases, these currencies are generally not convertible abroad, and/or the rules not always strictly enforced.