Marriage equality has arrived and it's not just for "the gays." Wedding customs are evolving for all. Wedding parties are progressing, as well, and the tradition of "boys on one side of the aisle, girls on the other" is being adapted so that each spouse-to-be gets to stand with his or her tightest pals — regardless of gender. But not everybody is ready for this party. Some guests see a bridesman or groomsgal and don't know what to do. Here are a few simple tips for managing OPA ("Other People's Anxiety") and performing at your very best.