The Vietnamese, not unreasonably, see tourists as wildly rich – how else could they afford to stop working and travel the world – and a first quoted price is usually pitched accordingly. It makes sense, therefore, to be prepared.
First of all, do your homework. Find out the approximate going rate, either from your hotel or fellow travellers, or from one of the increasing number of fixed-price shops – remembering to take into account the difference in quality, for example, between mass-produced and hand-crafted goods.
The trick then is to remain friendly and amused, but also to be realistic: traders will quickly lose interest in a sale if they think you aren’t playing the game fairly. Any show of aggression, and you’ve lost it in more ways than one. If you feel you’re on the verge of agreement, moving away often pays dividends – it’s amazing how often you’ll be called back.
Keep a sense of perspective. If a session of bargaining is becoming very protracted, step back and remind yourself that you’re often arguing the toss over mere pennies – nothing to you, but a lot to the average Vietnamese.