Pretty much the same as any Catholic ceremony :). The only thing to know is that only Catholics are allowed to take communion. Non-Catholics are welcome to receive a blessing during communion or you can remain in your seat.
The first thing you'll notice is that all guests will get the opportunity to take photos with the bride and groom when you get to the reception hall. The MC will call your group up one at a time so listen out! Once seated for dinner, the couple will greet each table ("chao ban"). Decide on one (1) person to toast the couple on behalf of your table. If you have red envelopes ("li xi") that you would like to gift to the couple, you can give them after the cheers. Also expect some karaoke, some dancing, and, of course, a lot of partying!
Red is an auspicious, lucky color in Vietnamese culture. Red envelopes with cash or checks are traditionally given to the couple during the reception as gifts (there are no registries in Vietnamese culture!) The giving of red envelopes is a way to symbolically bestow happiness, luck and good wishes to the couple. The photo above is an example of a red envelop ("li xi").
Shouting "Một, hai, ba, vô!" (pronounced "mot, hi, ba, yo") as loud as you can! This means "One, two, three, yo!" Synchronized drinking at it’s best!
There will be a 10-course Vietnamese meal. Vietnamese food is similar to Chinese and Thai food so many courses will look familiar. The meal will include some vegetarian dishes.
We are choosing to following the Vietnamese gifting tradition. See question above: "What is a red envelope?"