I second the idea to read the Unofficial Guide. It has fantastic touring plans, which park to avoid on what day, rundowns of restaurants, hotels...call it a Disney Bible if you will. I will say that some find it refreshingly honest while others say it is too harsh in its critique. Definately worth reading though.
The other thing to try is making meal reservations (called priority seatings or PS) in the disney resorts as this is a great way to see the hotels. Do a monorail tour of the various resorts one afternoon also.
As for the parks, please don't try to see every single attraction. You will kill yourselves with commando style techniques. Once you have read the official guide, pick and choose what is important to you. You have nearly 3 weeks so you can afford to have a park day followed by an off-day of shopping, water park etc.
Get hold of park maps so you know which way to head in the morning. Plan your first couple of attractions and get a fastpass for one while doing the other.
Try not to miss the evening spectaculars ( Illuminations, Fantasmic, Wishes) as these are real highlights.
Finally, read these boards like crazy, ask as many questions as you want ( there are no stupid questions and someone always knows the answer), read the trip reports to give you a feel for how people organise their day and have fun.
Welcome to the DIS! (Sorry about my answer, got a bit carried away)
Much pixie dust,
Claire