Make a big fuss over the Bride.
Don't gossip.
Don't speculate on the cost of the drinks, the dress, or the band.
Enjoy the party, for the sake of the Bride.
Tell the Bride she is beautiful.
Dance.
Talk to other people at the Wedding, especially the parents and close relatives of the Bride.
Show you are honored to be a part of the festivities.
Be sincere.
Come with the intention of celebrating the love of the Bride and Groom.
Don't drink too much.
Add to the love of the day.
