I agree with the others. Definitely try to stay at one of the hotels on the resort. Especially if you don't plan on going anywhere else but Disney world. You'll save a ton on gas and parking fees, not to mention the convenience of having the Disney shuttle taking you to and from each park right from your hotel.
We went two years ago in September, and I believe that's the best time of year to go. Not too hot, and the crowds and lines weren't bad at all. Since it's after Labor Day, most everyone is back to school. We didn't have to FastPass any rides/attractions. The longest I waited for anything was maybe 10 minutes at the most!
This to definitely not miss:
1. Mission Space @Epcot--Awesome ride!
2. The laser/light show @Epcot
3. Fireworks @ The Magic Kingdom
4. If you're taking children, get reservations for a character breakfast. They'll have a blast!
5. The Tower of Terror @Disney/MGM Grand.
That's all I can think of for now... If anyone can think of anything else, let's hear it!
