congratulations fifisworld
my wedding was my favourite day ever, just like rookiemaster
my main piece of advice would be similar to a lot of others: don't sweat the small stuff. This is all about you and your DP getting married surrounded by people you love, so as long as you manage to get married (actually I almost didn't even manage this bit ) then it's been a success.
If you know the basic outline of your day - ceremony, reception really you've done the biggest jobs. The only other things I spent any significant time on were guestlist/invitations and my dress fittings.
totally agree with MrsTittleMouse about having a small window of time to just take in the fact that you're married. The whole day is such a whirl that some quiet time is really special. Although you need to balance it with rookiemaster's advice not to leave people too long with no food and nothing to do.
Also, although Bumblelion is right about enjoying the day and not spending the whole time worrying if people are having fun, I would say beforehand try to be as accommodating of your guests and their requests/needs as you can. The more relaxed and welcoming you are to your guests the more they are likely to be relaxed and in good humour on the day.
That's it. Oh and try, if possible, not to have your bridesmaid chasing you around the house at 3am the night before trying to wrestle a bottle of champagne out of your hands and just go to bed as you are told.