Bring as little as possible, Vietnam has pretty much anything you can find back home.

Necessary documents: your  passport and  visa (with their copies); 2 photos (3cmx4cm), tour dossier (tour itinerary, address of travel agent or travel company operator, contact number… ) and others (if needed).

Cash in US$5’s, US$10’s, US$20’s and US$100’s (US dollars are commonly acceptable)

All the soaps and smellies are cheap and plentiful, and clothing, shoes and backpacks are all manufactured in Vietnam and available at a fraction of the price in the West. Tampons are available in all major towns and cities, but not in more remote areas.

A Swiss-army knife or equivalent come in handy, but you don’t need 27 separate functions, just one blade and an opener. A torch (flashlight) and compass are also useful.

Other handy things to bring are: name cards, as Vietnamese deal them out like a deck of cards; ear plugs to block the ever-present noise; a universal plug adaptor; a rain cover for the backpack; a sweater for the highlands and air-con bus trips; mosquito repellent to keep the bugs at bay; and a folding umbrella if you plan to visit during the rainy season (July and August are the wettest months).

The secret of successful packing:  plastic bags – not only do they keep things separate and clean, but also dry. That means a lot at the end of a long, wet day.

Luggage Packing tips

What needs to be brought in Vietnam?
- International Airline ticket
- Passport and photocopies of your passport
- Visa or Visa approval letter and some color passport photos (size 4x6cm) (at least 2)
- Insurance document (if any)
- Cash in USD or Euros (20’s and 100’s)
- Other equipment as follows;

General
• Duffel bag - waterproof and with a lock, or easily wheeled suitcase
• 5-6 zip lock bags (They come in handy for all kinds of uses.)
• Sun glasses or reading glasses
• Good walking shoes and sandal
• Good trekking shoes (for trekking tour) or slippers (for beach relaxing tour)

Optional

• Camera and film
• Mobil phone
• Head phone and your favorite music compact disc (CDs).
• Favorite Books/ Vietnam Guide book/Diary
• Biro pens, pencils, note book
• Pictures of your family

Basic Clothes

• Good walking shoes or cloth sneakers (They are light and dry easily. Good for driving.)
• 3-4 pairs of socks
• Polar fleece pullover or jacket or sweater (if travel in the north from November to March)
• 4-5 T-shirts or blouses
• Wide-brimmed sun hat
• Underwear (3-5 sets, depending on your desire to wash)
• Mid-calf lightweight walking skirts or dresses or loose pants (women)
• 1-2 bandannas
• Bathing suit
• Long-sleeved shirts
• Raincoat or poncho
Notes: Dress in Southeast Asia tends to be quite casual because of the warm, humid, tropical climate. For women, casual cotton pants and skirts are most acceptable for daytime wear, but bare sundresses and short shorts are frowned upon, especially in pagodas & temples.
A sweater, sweatshirt, light jacket, or fleece pullover is a good idea when visiting the northern areas in the winter (from November to March); and, it is useful to have a windbreaker or rain poncho as protection against the unexpected rain showers that tend to occur.

Health equipment and Medical Items

No actual vaccinations are officially required. Malaria prophylaxis is no longer recommended but visitors are advised to check with their doctors or travel immunization clinics regarding the advisability of inoculation against typhoid, tetanus, hepatitis A & B.
Carry a medical kit with bandages, splints and the like. However, the leaders (tour guides) are not permitted to dispense personal medicines to clients. It is important if you bring a complete, personal medical and first aid kit along with a few other essential items. Suggestion the following (Note: You will need to pack sharp objects in checked baggage due to tightened airline security):
• Aspirin or Tylenol Band-Aids and betadine ointment
• Throat lozenges and cough medicine
• Cold medicine and antihistamines
• Cipro - an antibiotic for indigestion
• Chaps tick
• Suntan lotion 100% UV effective (25 SPF or higher)
• Biodegradable soap (The blue bottles of Mountain Suds are excellent)
• Pack towel/washcloth
• OB tampons (women)
• Hand/body lotion
• Brush/comb
• Toothbrush/toothpaste
• Eye drops
• Facial breathing filters (optional for Kathmandu)
• Antiseptic toilettes
• Insect/ mosquito repellent
• Sewing kit with scissors, tweezers, and needle. (Note: You will need to pack sharp objects in checked baggage due to tightened airline security.)

Frequent Questions to answer:

What credit cards do I need to take with me?
Take your major credit cards, such as, Visa, Master Card and American Express.
Make sure they are really credit cards and not just debit cards with a credit card company’s logo on them. Many locations require a credit card and will not accept a debit card, so they may have limited use on your travel.
Leave all your local store credit cards in a secure location at home; there will be no need to carry them with you.

Why should I contact my credit card companies before I leave?
You want to notify them of your trip. They may delay you if they are unaware you are traveling. The unfamiliar spending patterns might cause them to suspect that the card is being used fraudulently and delay your approvals.
They will be able to explain many of the services that they can provide while you are on your trip.
How can my credit card company help prepare me for my trip?
You can arrange to pay bills that will come due while you are gone.
They will be aware that you will be making charges from another country.
They will be able to give you an idea of how acceptable their credit card is in that particular country.
They can verify acceptance at certain foreign locations.
They’ll be able to see if your PIN number will work in the countries you are visiting. They can also issue you another PIN number if your current PIN is unacceptable to the foreign bank’s system.
They can explain cash advance, ATM, foreign purchase and foreign exchange rate policies and fees.
They can explain any services they offer, such as, extra insurance for your rental car, luggage or purchases. Make sure the coverage offered extends outside the United States and will be valid in all the countries where you’ll be traveling. Also, be sure to note any other exceptions.
They may need to give you another phone number to call in case you need to reach them. The 800 number listed on the back of your card may not work from foreign locations.
You can find out if they charge a currency conversion fee, so you can find the most economical card on which to place your foreign purchases.
Should I use my ATM card while traveling?
Yes, you’ll have access to cash during your trip so you won’t have to take as much cash with you and using your ATM card can also be a good way to get cash in foreign countries.
The ATM will issue money in local currency.
You should exchange at the bank’s wholesale exchange rate. You may still want to shop around to different banks since some will charge a high usage fee for their ATMs. Although, even high ATM fees may be less than others will charge for currency exchanges.
Don't wait until you're out of money to go to an ATM, the machines can run out of money or break down.
What should I know about using travelers checks?
If the particular brand of travelers checks are accepted in the country you’ll be visiting.
How widely they are accepted within the countries you’ll be visiting.
Any fees for purchasing and using the travelers checks.
The travelers check company’s loss, replacement and refund policies.
How can I protect my travelers checks while traveling?
Take the same precautions you would to protect your cash. Be sure to learn and follow the procedures required if you lose your travelers checks. You’ll also need to make copies of your travelers checks before you go and keep separate from them the following information.
The serial numbers of the travelers checks.
The denomination of the travelers checks.
The date and location of their purchase.
The phone number to call to report them missing.
Source:  http://www.alltraveltips.com/