Definately comfy shoes!! and like Ashley said a game plan - i find that if you dont have some sort of itinery you always "miss" something - but then i always seem to go back sooo..?
Don't forget your on vacation. There is a lot to do and see at disney and if your there fore you wedding on top of it you need to make sure there is time in your game plan to relax. Going home more tired then when you left makes it hard to face the real world.
I have to second Kellykins. We are having a day where we are kind of taking it easy. We're going to take a Segway tour of Epcot, get a couples massage, and just swim at the resort. My fiance made me extend our trip by a couple of days so we didn't feel rushed to get everything in.
Take comfortable shoes. The first time I went I took a pair of Brand new shoes and ended up with blisters from not having them broken in. I also got sunburned so I learned that no matter how long I was going to be in the sun, I needed to wear sunscreen- I am very light complected and burn very easy. I also took several hairties since everytime I straightened my hair it went curly and frizzy because of the humidity.