Most people from developed counties find these issues very difficult. There are no set rules, but the following information and advice may be helpful.
The prices for goods in supermarkets, pharmacies, restaurants, hotels, official transport, basic commodity shops and so on, are usually fixed. Those for fresh fruit, vegetables and flowers from street sellers, motorcycle taxis (’xe oms’), bicycle taxis (‘cyclos’), souvenirs, clothes (especially in tourist areas), and goods bought from peddlers are usually variable. To barter effectively, laughter and good humour is an essential prerequisite. When an initial price is quoted, throw up your hands in exaggerated horror and offer between a third and a half. You can then negotiate towards a fair price. Walking away will usually determine whether the last offer really is the last. Please remember that many of the people you deal with will be poor, so driving them down to an unreasonably low price is unfair. On the other hand, paying an unrealistically high price will encourage the recipient to regard foreigners as easy targets and inflate prices even further. Postcards from postcard sellers are almost invariably overpriced – buy yours from a shop!
Taxi fares are nearly always metered, (although the accuracy is sometimes questionable), but it pays to negotiate a fixed price for long journeys. For xe oms and cyclos, always agree a price in advance. If you want one of the many young boys who tour the streets with a box of brushes and polish to clean your shoes, fix the price in advance, make sure that they stay within eyesight and don’t pay for any ‘repairs’ without agreeing the cost beforehand.
You may come across some remnants of an earlier dual-pricing system that is gradually being phased out. If so, it isn’t local people trying to make a fast buck, but simply an official recognition of the considerable income gap between you and the average Vietnamese citizen.
While recognition of particularly good service is universally welcomed, there isn’t a general culture of tipping in Vietnam. There are a few exceptions. Tourist guides traditionally rely upon tips to build up their wages. As a rough guide, $5.00 per day would be about right for a good job, perhaps more for something special, with less than a day at a pro-rata rate. Porters at railway stations rely upon small tips for an income, but taxi drivers will normally help you with luggage as part of their service, unless you have something particularly heavy or difficult to carry. If you’re in a hotel for a few days or more, a tip for your chambermaid or anyone else who has been helpful would be appreciated.
You’ll find a distinct difference between the North and South of Vietnam. Saigon’s exposure to US culture has created more of a tipping culture, so expect to pay more, and more often!
Beggars are common in Vietnam, but in tourist areas, only a minority are genuine. Grubby children with soulful eyes are usually working for a begging syndicate, and young girls and women carrying very young babies have often rented them for the day from a friend. You won’t be bothered often, but if approaches are made, ignore them, or complain to a police officer if they annoy you. Giving money to fake beggars only swells their ranks.
However, there are deserving cases. Elderly widows, invalids, amputees and Buddhist monks usually have no other source of income. If in doubt, see if they approach Vietnamese people, and what the response is from them. If you do decide to give them money, keep the amount small. Excessive generosity will attract other less-deserving beggars immediately. For visits to SaPa and other places where small children can be a nuisance, sweets are a good alternative to money (and almost as acceptable)!