I don't ever make "I speak for everyone in the group" statements, but here I will.
Brides: Stop putting your bridesmaids in expensive dresses they will never wear again. 6 months from now, nobody will remember that you had 8, perfectly-paired, chiffon-draped ladies in your party except for you. 6 months from now there WILL be 8 ladies with $200 chiffon dresses in their closets that they LITERALLY can't ever use again... because they look like bridesmaid dresses. Be kind. Pick something fun that they can wear again or let them pick their own. informal style garment for mother of the bride
Grooms: Stop renting tuxedos and let your groomsmen buy matching tuxes or suits. Buying a brand-new, already tailored-to-fit tuxedo, that they get to keep after your wedding, is anywhere from $50-$100 cheaper than what you're making them rent. And then they'll have a tux in their closet for future events, which is cool.