Visa
Visa are required by all nationalities. Regulations and costs change from time to time so it is advisable to check the current rules. Visa are refused without explanation to those the authorities consider a proscribed profession. It is also a good idea to carry 2-4 passport sized photos with you when traveling to Vietnam, as sometimes these are requested by Immigration officials. Those who travel overland from Cambodia will be crossing at Moc Bai border gate, from Laos at Lao Bao and Cau Treo border gates, from China at Hakau, Huu Nghi and Mong Cai border gates. You must ensure your visa specifies entry  " international border gates". Further more your visa must be " multiple entry " If you want to fly out from Hanoi or Saigon after your  extension trip to Angkor Wat or Luanprabang.

Currency
The local currency in Vietnam is Vietnam Dong ( VND ). At the time of writing, 1 USD is around 15,000 VND. Local VND or USD are both accepted. Banks are open Monday to Friday and some open on Saturday morning. In main cities, travelers' cheques can be exchanged at banks and some exchange bureau, but this can be very difficult in small towns. ATMs can  be found in major citiesHanoi and Ho Chi Minh city, Hoian, Haiphong so do not depend on any kind of bankcards ( e.g. credit cards...) as your main source of funds.

Transport
On entering Vietnam all visitors must complete an entry/exit card ( white/blue color ) and a customs declaration form ( white/yellow). It is important that you keep both of these forms and present them to Customs and Immigration upon arrival. If you have booked an arrival transfer or are on one of your designed group tour, please look for our representative who will be holding a sign with your name on at Hanoi or Ho Chi Minh city airport.

Taxi: If you have not arranged for  an arrival/departure transfer, you can always take a cap which is available at the airport  and at the hotel. Whether you are arriving at Hanoi or Ho Chi Minh city it is best to take a metered taxi to the hotel. Driver may want to negotiate a price before leaving the airport, but do not agree to this. Rather you should make sure they switch the meter on and pay the amount it displays when you reach your destination. Taxi fares vary according to the type of vehicle ( i.e. a modern A.C car is more expensive than an older non A.C vehicle ). As a guideline you should expect to pay the following amounts for a taxi  from the airport to your hotel:
                        Hanoi:            $ 10-15 US
                        HCM city         $ 7-10  US
During your free time there may be occasion to use local taxis. These are inexpensive, about 5,000 VND for a first km.

Telecommucation
Most hotels now have IDD phones in rooms and it is possible to send faxes from hotels and post offices although be warned these services are expensive . Away from the major cities it may not always be possible to make international calls. Cyber cafes are becoming popular in the major cities in Vietnam, and many travelers now prefer to keep in touch by e-mail. Post cards can be bought at all the main tourist sites and stamps are available from post offices and some hotel reception desks.

Electricity
The voltage in the cities and towns is generally 220V, 50 cycles, sometimes 110V in the rural areas. Electric sockets are standard European or American. If you bring a computer to Vietnam, you must use a surge suppresser to protect your circuits. Large  voltage regulators can be bought at computer stores in Vietnam to give greater protection. It is a good idea to bring adapter plugs in case your plugs do not fit the sockets, which are sometimes two round pins, other times three pins. If you do not have the correct size plug, however, it is easy to buy one at many markets or electronics stores. Batteries are available in the major cities.

Business hours
Offices are usually open Monday to Friday from 8:00 until 17:00 or 18:00, and some also open on Saturdays.
Most shops open 7 days a week around 9:00am until late as 20:00 or 21:00.

Food
Vietnamese food comes as a wonderful surprise and is definitely not to be missed! It has a very distinctive style, although it is also clearly influenced by Chinese and , to  a lesser extent, French cuisine.
Meals will usually include rice or noodles as staples along with a vast array of vegetables, and meats like chicken, duck, beef and pork. Dishes feature a wonderful fusion of flavors and you will find that fish sauce is a condiment accompanying almost every meal. Anther unexpected delight is the availability  of good quality seafood ( fish, calamari, prawns and crabs) which is caught along Vietnam's extensive coastline.
Freshness is of paramount importance in Vietnamese cooking, so ingredients are bought fresh from local market on a daily basis.
The fact that many Vietnamese are completely omnivorous, has lead to some very exotic dishes - such as barbecued frog legs which can be found in food stalls in many local markets ( perhaps this is how the French come to introduce frog legs into their cuisine).
On the other hand, there is also a strong Buddhist influence in Vietnam which means that vegetarian food is also widely available.
Here are just a few examples of the fantastic dishes you can expect to find in Vietnam.

Some of the legacies left over from the French colonial period include crispy baguettes, pate, hard boiled quails eggs, crème caramel, and banana flambée
On the subject of deserts, we should point out that they are not particularly common. However an amazing assortment of fresh tropical fruits is usually on offer, which will round off a meal perfectly.

Drinks
Tea, similar to Chinese green tea, is one of the most common drinks in Vietnam. Coffee was introduced by the French and is very good. It is thick and strong and is served complete with drip filter, so you know it is fresh! If you ask for milk it will usually be sweet condensed milk. Home brewed rice wine is often offered to guests, but  watch out - it is extremely alcoholic! Light larger style beer is more commonly available, Ba Ba Ba, Hanoi beer being the most well known local brands. Spirits, such as nep moi ( a type of Vodka) , are also produced locally but once again, be cautious as these are very strong.

Water
It is not advisable to drink tap water in Vietnam, but bottled mineral water is safe and available everywhere. Ice in drinks is generally OK in good standard hotels and restaurants but it is best to avoid it on street stalls or in country areas.

Health
Malaria: Malaria is not a problem in big cities, but care should be taken in remote areas, especially in the rainy season when mosquitoes breed. If spending time in the countryside (below 1,200 meters al), contact a doctor about anti-malarial drugs. Try to avoid getting bitten, cover up after dark, wear insect repellent, burn mosquito coils and sleep under a net.
Diarrhea: This malady is common. If it occurs, maintain a diet of bland foods of fluids only. If severe, consult a physician.
Pharmacies: Many of the drugs sold in small pharmacies are copies of have expired. Stick to reputable.

Shopping
Vietnam offers a wide range of souvenirs and shopping in the various local markets around the country can be great fun. Good bargaining skills are essential and as high quality souvenirs or genuine antiques are difficult to find, prices should generally be low. Here are some of the items which make their way onto many people's shopping list: Clothes ( e.g. T-shirt, polo-shirt, trousers, shorts, skirts,) beaded shoes, conical hats, single-cup coffee filters, sleeping bags, CDs,  embroidered table cloths, carving in wood or marble, lacquer ware ( e.g. pictures , trays, trinket boxes), and traditional style paintings and sketches. Handicrafts produces by the people of the hill tribes in the north are also very popular. These include fabrics, jewellery, embroidered bags, and wickerwork. It is also possible to buy tailor-made cloths. These are made to order and are usually available for collection within 24 hours. Once of the best places to buy tailor made items is Hoian.

Language
As Vietnamese has six different tones, it is a difficult language for most foreigners to grasp. The same word can have six different meanings pending on the tone used to pronounce it.  Nonetheless we encourage you try to speak a few words of the local language. The locals will certainly appreciate your efforts!
Although Roman script is used for modern Vietnamese, the words and phrases below are spelled phonetically to help you with pronunciation.

Number:

Public Holiday
New Year's Day 1st Jan
Liberation of Saigon 30 April
International Labor Day 1 May
Birthday of Ho Chi Minh 19 May National Day 2 Sept

Vietnamese New Year or Tet is celebrated each year with an official 3 day holiday, but some businesses close for an entire week. The actual dates of the Tet celebrations change from year to year in accordance with sometime in January/February.
 
Suggested Reading
Rough Guide to Vietnam
Lonely Planet Vietnam
Vietnam Handbook
The insight Guide to Vietnam
Fordord Vietnam
Background reading:
Vietnam, a History ( Stanley Karnow ) an Historical
Account of the Vietnam war
Child of War, Woman of Peace ( Le Ly)
The sorrow of the War ( Bao Ninh)
Three Moon in Vietnam ( Maria Coffey)
Down highway one ( Sue Downy )
Great Railway Bazaar ( Paul Theroux )