If you're a beer lover, you'll love Vietnam. It's very much a beer culture, and Vietnamese food is made to be drunk with beer. Local Vietnamese beer is very cheap and easy to obtain, and you shouldn't miss the local varieties, which you will almost certainly be offered with your meals.
When purchasing fish sauce for your Vietnamese food, look for the words "thuong hang" or "nhi" on the label. This indicates that the sauce came from the first pressing of the fermented fish of which it was made. It should also exhibit a light amber color.