1) A white dressIt may seem like an outdated rule, but it still applies. I don't care how much your dress doesn't look like a wedding dress, white is reserved for the Bride that day. Wearing HER colour that day would be just rude. And with so many other colour choices out there, just don't do it.
2) Anything Bridal-like
In other words, anything so flashy that it may outshine the Bride (or the Bridesmaids). In case you're not sure what that would be...it means anything shiny and sequined, anything with lots of tiers or ruffles, or anything with a bustier like top. Get it?
3) Super Sexy
I don't care how smokin' your body is, there is a time and a place for your sexy, over the top dress. And today is not it. Save your cleavage revealing, too short, too tight dress for the Stagette.