Do not hit on the bride and bride. This also goes for groom, and groom or bride transitioning and groom transitioning into bride or the groom/bride/whatever-I-do-what-I-want.
Do not call attention to how uncommonly pretty the wedded lesbians may be. Do not say, "You don't look like lesbians. You're so pretty! Look at these pretty lesbians, everyone!" This sort of behavior may be more acceptable with gay men.
Do not tell a story about how you "used to be gay."
Do NOT say you are a lesbian trapped in a man's body. Do not wear this T-shirt to the wedding in lieu of saying it.
Do not say you wish you were gay because it would make life easier. No. You're wrong. Stop.
Queer people are permitted to bestow the title of "honorary gay" upon their straight friends, but no one is ever permitted to bestow this title upon themselves.
Don't try to have your bachelorette party at a queer wedding. I know you love dancing, but there are other places to dance.
The wedding is not an educational institution. If you have a burning question about queer life, Google it beforehand.
If something about the wedding confuses you, try to find a more liberal friend/family member to whisper-splain. Men are kissing men, is that normal? Yes, that is normal. This beautiful-looking drag queen has been doing an R&B soul version of "Born This Way" for over 45 minutes. Is that normal? Yes, that is normal.
Drag queens are encouraged to be considerate of the bride when considering what to wear. I know it's hard being so fabulous.