1. If you plan to drink at all, consider doing shots. I tried wine and beer, but had to keep putting my glass down to hug or talk to people all night. Eventually, I resorted to shots, since they were quick!
2. Relax. If it's going to go wrong, it's going to wrong, and there's nothing that you'll be able to do about it that day. Enjoy yourself. Chances are that if something does go wrong, no one but you will notice anyway.
3. The day will fly by. Be sure to take time to come up from the chaos and just enjoy what's happening around you.
4. The day is about YOU and your DH. Just remember that and enjoy each other. People will be grabbing at both of you and fighting for your attention all day and night. Take time for each other that day. It's very easy to get separated.
And the best advice we pass along to everyone....
5. Use your DJ or band leader to control your reception and keep you on schedule. Ex: if you plan to go table to table to greet folks at the reception, pull your DJ aside and quietly put a time limit on it so that you're not spending all night doing that. If the DJ is pulling you away, then it's not your fault and your relatives can't complain.

;-)