As I have been travelling down Vietnam, I have been thinking about the possible reactions of my friends and family as they come to visit Vietnam. If they have travelled much in South America or other parts of Asia, for example, they will not be too surprised. The tolerance of other standards of things like cleanliness is important. So is a spirit of adventure to try new things like foods you don't recognize.
But the Our Man in Hanoi blog has said it much better than I can. PLEASE read this posting in his blog as you think about coming to Vietnam (or other Asian countries like Cambodia or Thailand). Click this link for his posting.