I assume you will be going to reception and not the wedding itself.

1. Long pants, shoes and socks, and a collared button shirt is the appropriate attire for men. Women use weddings as an excuse to buy a new dress, get a hair do and wear make-up.

2. As the manager of the bride a $50 or $100 gift in cash would be typical. The wedding invitation should include an envelope for the gift.

3. Expect to drink a lot of beer.

4. Memorize the phrase Một hai ba, yo.

5. Be prepared for bad karaoke and Vietnamese polka music.

If you can go to the actual wedding that's a little more interesting and more traditional.