Accommodation is a concern of every traveler, whether looking for a place to pitch a tent or a luxury suite in a fancy resort. Booking accommodation, dealing with the vast array of accommodation options, and considering alternative lodging options are all issues that travelers face.
You might have to change or cancel a reservation, for example if your plane/train/bus is delayed or cancelled and you therefore arrive a day later.
Depending on how you booked the accommodation, you may be able to contact the hotel or pension directly by phone to make the necessary change/cancellation. If it was booked through a travel agent or consolidator, you may need to go through them.
Pay attention to the cancellation policy when you make the reservation. Most hotels will require a credit card number to guarantee the room. They will usually charge you for one night if you cancel less than 24 hours before arrival. In some popular tourist destinations such as Hawaii or Las Vegas, this minimum notice may be as long as 72 hours, or you may be charged for the entire stay. This can happen even when you make reservations through a travel agent and your delay is caused by transportation also arranged by that travel agent.
Newly opened hotels. Frequently, the best hotels are those just opened. Beyond being new and modern, they need to attract clientele, and may strive to offer more comfort or services for less money. It often makes sense to inquire locals upon arrival which hotels / pensions etc have opened in the last year or two.
Last-minute offers. Many hotels discount their unsold rooms and sell them through specialist 'last minute' type consolidators. The reduced rates available from these consolidators are not usually advertised in the hotels themselves (the hotels do not want to advertise these lower rates to guests who are paying full rates). Contacting a consolidator directly can save you money and, especially in larger cities, legwork - the better companies will usually telephone the hotels within your budget to confirm availability, important when you've got tired legs in a large city like London for example. Look for consolidators offering a telephone as well as online booking service so you are not dependent on internet access when trying to find a hotel.
Types of accommodation
Hostels (more commonly referred to as "youth hostels") are a loosely-defined form of guesthouse, generally low-budget compared to other places to sleep. Although often used by youth there is usually no upper age limit.
Capsule hotels are probably the cheapest accommodation you can get in Japan. The "rooms" are little more than small one-person capsules with only a mattress, radio, and TV. Note that most capsule hotels are segragated by gender.
Bed and Breakfasts (B&Bs) and Guesthouses provide hotel style rooms. However, they are typically smaller residences and you will interact with your hosts and other guests, often eating together and sharing common spaces. Bed and Breakfasts and Guesthouses are found both inside and out of major centers. Many market themselves as providing a "quiet escape". There are many associations and websites that offer help finding a Bed and Breakfast in your travel area.
A hospitality exchange or home stay network is an organization that connects travelers with local residents in the cities they're visiting. If travelers can connect with the right people at the right time, they can get room and sometimes board in the place they're visiting for free or at a deep discount. Network size goes from a few thousands to a hundred thousands, and most networks are growing steadily.
Car camping, Caravaning, RV camping... it goes by many names, and the experience varies widely, but this form of camping involves carrying your equipment in your motor vehicle, which you drive right to your campsite. Unlike more traditional camping, car camping allows you to carry quite a bit more equipment, and the focus is usually to enjoy the site, cook-outs, day hikes, and other outdoor activities. Some just use their vehicle for transportation, pitching a stand-alone tent to sleep in. Some use it to pull a pop-up trailer/tent or use their car or van as part of the tent or shade structure. Some drive large vans or recreational vehicles to sleep in, which may include many of the comforts of home (on a more compact scale).
Camping is do-it-yourself accommodation: you carry your roof and your bedding in your backpack or your car. It's often the only choice of accommodation you have when you're travelling off the beaten track, but there are also very popular sites for camping holidays. Always check whether you need a permit to camp, how much it costs and whether your choice of site will be restricted. Many popular national parks or protected sites have limited camping to particular sites and some have banned it altogether. When hiking, there will often be set campsites a day's walk apart, and often you are forbidden to camp between them. Permits can typically be obtained in advance or on arrival, but may be hard to get or sell out during very popular holiday periods - don't blithely plan a Christmas camping holiday without being sure you can get a permit if you need one.
Vacation rentals. Many residents of popular tourist destinations lease their houses and apartments to vacationers. The residence may have been bought specifically for this purpose or the normal occupants may vacate it during some parts of the year. The guests will have full use of the residence, usually with utilities included but no servicing or meals. This approach can be cheaper than booking a hotel room for the same length of time, especially if travelling with a family or other sizable group of people. Facilities will vary depending on the property, but usually include kitchen and laundry facilities and possibly amenities like a swimming pool (or access to a communal pool), a games room (table tennis, pool, Playstation 2, X-Box, ...), and TV/video/DVD players. Contacting the owners directly is the ideal way to make arrangements as they can answer any questions you may have about the property, and may offer more competitive pricing since there's no middle-man.