Ho Chi Minh City's Tan Son Nhat Airport is Vietnam's busiest international air hub, followed by Hanoi's Noi Bai Airpot. A few international flights also serve Danang. Bangkok has emerged as the principle embarkation point for Vietnam but it's still possible to get direct flights from a number of major Asian cities and a few Australian cities. Buying tickets in Vietnam is expensive. Departure tax is US$14.00 , which can be paid in dong or US dollars.
There are currently 10 overland border crossings for travellers coming to Vietnam, but more may open soon. All crossing points suffer from heavy policing and often requests for 'immigration fees'.
For getting to/from China, it's become very popular to cross the border at Friendship Pass, or Dong Dang, 20km (12mi) north of Lang Son in northeast Vietnam, to get to/from Nanning. There is a twice-weekly international train between Beijing and Hanoi that stops at Friendship Pass. The other popular border crossing with China is at Lao Cai in northwest Vietnam, which lies on the railway line between Hanoi and Kunming in China's Yunnan Province. There's also a seldom used crossing at Mong Cai.
It's possible to enter Laos from Lao Bao in north-central Vietnam; there's an international bus from Danang to Savannakhet (Laos). The other crossing is at Keo Nua Pass/Cau Treo, west of Vinh and Nam Phan/Na Meo near Mai Chau. There are three crossings to Cambodia. Bavet/Moc Bai links Phnom Penh with Ho Chi Minh City and the road is in reasonable shape now. There are also two crossings in the Mekong Delta, a river crossing at Kaam Samnor/Vinh Xuong and a land crossing at Phnom Den/Tinh Bien.
Vietnam Airlines has a near-monopoly on domestic flights, which are relatively expensive. The departure tax on domestic flights is about US$1.50 , payable in Vietnamese dong only.
Ultracheap buses and minibuses criss-cross the country in an impressive network of routes. These are smarter, faster and safer than they used to be and are a good way to meet locals. The alternative, used by many foreigners, is to charter a minibus. They cost more can be faster as they don't stop as often; ask at budget hotels and cafes for details.
While sometimes train travel can be slower than bus travel, it is safer and more relaxed, and you're likely to have decent legroom. There are several types of train, including the famous Reuinification Express ; but think twice before you take a crowded, snail-paced local train. Petty theft can be a problem on trains, especially in budget class. Children throwing things at carriages, everything from rocks to cow dung, is another problem, and you're advised to keep the metal shield on the window in place.
Hire cars and drivers are available at reasonable prices. You'll still be stopped by the police to pay all sorts of 'fines', but at least you'll have a local with you to do the negotiating. You can hire a motorcycle to drive yourself if you have an International Driver's Permit endorsed for motorcycles, but you'll need nerves of steel.
Travelling through Vietnam, and around the towns and cities, by bicycle is worth considering, though the traffic is still a hazard on highways without wide shoulders. Trains and buses will carry your bike when you want a break.
Other than the sophisticated local bus networks in Hanoi and Ho Chi Minh City, local transport is by taxi (some metered, some not) or cyclo (pedal-powered vehicles that are cheap and plentiful). If you're in a hurry, and fearless, try flagging down any passing motorbike. Many people will be happy to give you a lift for a fee a little higher than the equivalent cyclo fare.