For western visitors, even those who have visited other Asian cities, Phnom Penh can be a bit of a shock. It is very hot and (in the dry season) dusty, its infrastructure is undeveloped, and it is a very poor city - much poorer than, for example, Bangkok or Saigon. The visitor who cannot adjust to rubbish filled streets, fluctuating electricity supply, and large numbers of beggars, should probably give Phnom Penh a miss.
Those who find themselves struggling with Phnom Penh's current state should recall the terrible times the city has been through in recent decades. In 1975 it was choked with up to 2 million refugees from the war between the then U.S.-backed government and the Khmer Rouge. After its fall to the Khmer Rouge in April, it was completely emptied of civilians and allowed to crumble for the next four years. Most of the already small class of skilled professionals were murdered or driven into exile. The city fell to the Vietnamese Army in 1979, but the new Cambodian government had no money to spend on urban improvement until the peace settlement of 1992.
As Cambodia's economy has recovered a new rich class has arisen in Phnom Penh, and a crop of new hotels and restaurants has opened to accommodate them and the tourist trade. But there is as yet very little between the extremely rich and the extremely poor. Tourists often have little choice but to stay at expensive hotels and eat western food, since Phnom Penh has not yet developed the capacity to provide cheap but clean accommodation or cheap but safe local food. All the guide books warn the visitor against eating food bought from street stalls, and the visitor sees at once why.
Don't bother with the Cambodian riel - the Cambodians don't. Take lots of low denomination U.S. dollar notes and everyone will be happy. The basic price for everything in Phnom Penh is "one dollar, one dollar."
Phnom Phen Pochentong Airport(PNH) is Cambodia's largest international airport and most flights into the country pass through there. Daily flights arrive from Southeast Asia's travel hub, Bangkok, as well as Saigon and Hanoi in neighbouring Vietnam. There are limited flights from Laos. Airlines include Bangkok Airways, Lao Aviation, Shanghai Airlines, and Thai Airways. The airport has a post office, bank, restaurants, Duty Free shop, news stand, tourist help desk, and Business Center.
Taxis from the airport run about $7 US. For visitors on a budget without a lot of luggage, it's worth walking out to the main road to catch a moto-taxi for $1-2.
Visa's are available on arrival for many nationalities.
There is extensive bus service to Phnom Penh from both Thailand and Vietnam, as well as Siem Reap (Angkor Wat) in the north. To the south there are regular services to Sihanoukville. Many buses and "mini-buses" (usually 10 person vans with 14 people in them) cater exclusively to western tourists. Buses are the most affordable option, but expect delays and close quarters. The main bus station is near the Central market where tickets can be bought (normally without any hassle).
A range of seasonal ferries ply the river between Phnom Phen, Siem Reap in the north, and the southern coast. These are usually much more scenic than the bus ride, but run in $20-$30 range. If taking the speedboat to or from Siem Reap (staging point for the Angkor temples), you have the choice of sitting inside or outside. If you sit inside you may get seasick. If you sit outside you will get both soaking wet and sunburned.
Phnom Penh now has plenty of taxis, and the service is fairly reliable. They are much the safest way to travel at night.
The Cambodian version of the tuk-tuk consists of a motor-cycle with a cabin for the passenger hitched to the back. They are cheaper than taxis, but the state of the roads makes travel by moto a dusty and bone-rattling experience. There are also hordes of young men on motorcycles who will take you anywhere for a small fare. This is quickest way to get around, if your nerves can stand it.
Phnom Penh's streets and footpaths are rutted and pot-holed, and are clogged with garbage, stagnant water, parked motos, sleeping people, livestock and building materials. This makes walking anywhere a challenge. The safest place to walk is usually in the middle of the road. There are not many cars and the motos will drive around you. Phnom Penh has almost no street lighting off the major boulevards and walking at night is not recommended.
Phnom Penh offers some interesting culinary treats you won't find elsewhere in the country. Many of these include French-influenced dining as well as Thai, Vietnamese, and modern takes on traditional Cambodian dishes. The standard pizza-banana pancake-fried rice backpacker fare is also always easy to find.
The best area to wander is along the riverfront where everything from stand-up stalls to fine French bistros can be found. Take great care eating from stalls, however. Peeled fruit and vegetables and anything uncooked should be regarded with suspicion.
There are a variety of places to stay although most fall into the following categories: 1) By the lake (apparently very cheap to stay so lots of backpackers) 2) By the river along Sisowath Quay - lots to see, and 3) Elsewhere in the city - again a large selection to choose from.
Take normal sensible precautions about walking down dark alleys at night and carry only the money you need when you are out and about - leave the rest (plus passport etc) at the hotel.