Travel in Vietnam

By plane
Flights are the fastest way to travel the distance of this long country; the trip from Hanoi to Ho Chi Minh City (HCMC) will take about 2 hours by plane. See Vietnam domestic flights, fare and timetable
By train
Although more expensive than buses, trains are undoubtedly the most comfortable way to travel overland in Vietnam. There is one major train line in Vietnam, the 1723-kilometer trunk between Hanoi and Ho Chi Minh City, on which the Reunification Express runs. Ho Chi Minh City to Hanoi is more than 30 hours, and overnight hops between major destinations are usually possible, if not entirely convenient. It's a good way to see the countryside and meet upper-middle class locals, but unless you are traveling in a sleeper car it is no more comfortable than buses. Trans-Vietnam train information
AC Soft or hard sleeper is recommended, and purchasing as early as possible is a good idea as popular berths and routes are often bought out by tour companies and travel agents well before the departure time (hence being told the train is sold out at a station ticket window or popular tour company office does not mean there are no tickets available-they've simply been bought by another reseller). Booking at the train station itself is generally the safest way, just prepare on a piece of paper the destination, date, time, no. of packs and class. However, unsold tickets can often be bought last minute from people hanging around at the station-a train is rarely sold out for real, as the railway company will add cars when demand is high. Commissions on these tickets will drop away as the departure time draws nearer.
In addition, there are shorter routes from Hanoi leading northwest and northeast, with international crossings into China. One of the most popular of the shorter routes is the overnight train from Hanoi to Lao Cai (with bus service from Lao Cai to the tourist destination of Sapa). See Hanoi Sapa tourist trains
Always try to buy your tickets at least 3 days in advance, to avoid disappointment, especially during peak holiday season, during which you should try to book at least a week in advance.

By car
International driving licenses are not accepted in Vietnam. The concept of renting a car to drive yourself is almost non-existent, and when Vietnamese speak of renting a car they always mean hiring a car with a driver. (After a short time on local roads with their crazy traffic, you will be glad you left the driving to a professional.) Since few Vietnamese own cars, they have frequent occasion to hire vehicles for family outings, special occasions, etc., and a thriving industry exists to serve that need. Vietnamese can easily charter anything from a small car to a 45-seat bus, for one day or several. Few drivers speak any English, so make sure you tell the hotel/agent exactly where you want to go, and have that communicated to the driver.
It's also possible to hire a car and driver for inter-city travel, at somewhat higher cost. Long distance travel by car may be a good choice for several people traveling together, as it provides a flexible schedule and flexible access to remote sites. Keep in mind that long-distance road travel in Vietnam by whatever means (bus or car) is slow, with average speed less than 50 km/hour. Highway 1, the north-south backbone of the country, is a two-lane road with very heavy truck and bus traffic.
Generally speaking, describing Vietnamese driving habits as atrocious would be an understatement. Road courtesy is non-existent and drivers generally do not check their blind spot or wing mirrors. Vietnamese drivers also tend to use their horn very often to get motorcyclists out of their way. In addition, most roads do not have lane markings and even on those that do, drivers generally ignore the lane markings. As such, driving yourself in Vietnam is not recommended and you should leave your transportation needs in the hands of professionals. Vietnam car rental service
By bus
Long-distance bus services connect most cities in Vietnam. Most depart early in the morning to accommodate traffic and late afternoon rains, or run overnight.
Public Buses travel between the cities' bus stations. In bigger places, you often have to use local transport to get into the city center from there. Buses are generally in reasonable shape, and you have the chance to interact with locals.
Open Tour buses are run by a multitude of tour companies. They cater especially to tourists, offering ridiculous low rates (Hanoi to Ho Chi Minh City: US$20-25) and door-to-door service to your desired hostel. You can break the journey at any point and continue on a bus of the same company any time later, or simply buy tickets just for the stage you're willing to cover next. Note that if you're not planning to make more than 3-4 stops, it might be cheaper to buy separate tickets as you go (ie Hanoi to Hue can be had for as little as US$5). Most hotels and guesthouses can book seats for any connection, although you're better to shop around at travel agents, as prices will vary on any given ticket/bus company. Going to the bus company office may net you a commission-free fare, but most major bus operators have fixed pricing policies, which can only be circumvented through a travel agent.
Since tour companies charge very little, they do make commission on their stop-offs which are often at souvenir shops, where you do not have to buy; they always have toilets and drinks and water available for purchase. The estimated time for a bus trip will not be accurate and may be an additional couple of hours sometimes, due to the number of stop offs. Collecting the passengers at the start of the journey can also take quite a while too. Always be at least half an hour early to catch the bus. Try not to drink too much water, as rest stops, especially for overnight buses, may be just somewhere where there are a lot of bushes.
Vietnamese buses are made for Vietnamese people - bigger Westerners will be very uncomfortable, especially on overnight buses. Also, many Vietnamese are not used to riding on long-haul buses, and will sometimes get sick - not very pleasant if you are stuck on an overnight bus with several Vietnamese throwing up behind you.
Even if you are sometimes bus-sick, it is advisable to book a sit at the middle rather than at the front of the bus. First, you will avoid viewing directly the short-sighted risks the driver is taking on the way. Second, you will somewhat escape the loud noise of unceasing honking (each time the bus passes another vehicle, that is about every 10 seconds).
Although the bus company will usually be happy to collect you at your hotel or guest house, boarding at the company office will guarantee a choice of seats and you'll avoid getting stuck at the back or unable to sit next to your traveling companions. The offices are generally located in or near the tourist area of town, and a short walk might make your trip that much more pleasant.
A scam that you may encounter is that after arriving at your location, the guides will ask you whether you have booked a hotel. Even though you haven't, say that you have and prepare the name of a hotel. If you say you have not booked one, they will charter a taxi for you and probably drop you at a hotel which they can collect commission. If you decide not to stay, things may get a little ugly, as they will demand that you pay the taxi fare, which they may quote as several times the actual fare for a ten minute ride.

Source: wikitravel