There's an enormous amount of printed and online information out there. When I plan my vacation, I do the following:
First figure travel mode. If I'm flying, I won't get a hotel until I have a date and a way to get there and back. Air tends to fluctuate the most.
Get a hotel, once you know when you're going to be there.
Then, I plan my 'strategy.' I find when EE is taking place and avoid those parks. I also use my previous experience and any online information available to avoid "known trouble spots," which generally means MK on Saturday night, but also includes things like CM nights at PI. I'd say books aren't the best source for this information, because it changes so much these days. So choose your parks according to what you want to accomplish vs how many people are trying to accomplish the same thing the same day. If we're eligible for EE, I use it, but then get out of dodge to another park by around 10 AM.
Also allow flexibility, to leave a park if it's getting beyond your comfort with the crowds. Two givens: children will always want to spend a lot of time in MK, so keep that in mind, but also keep in mind that when all heck is breaking loose across the entire Disney nation (crowd-wise), Epcot is always managable, due to it's size; the enormous amount of attractions (I consider the countries attractions, some don't); and the fact that being the restaurant capital of Disney, a lot of people are in restaurants at any one time.
Once we've chosen our parks, we choose priority seatings. Note that with stuff like Hoop Dee Doo, you need to make that soon, like right now. They actually take your CC for this, and if you change your mind, you have to cancel within 48 hours. But line yourself up some places to eat. We start doing this shortly after we're inside two months (but I book Hoop Dee Doo ASAP, I think they takes ressies up to two years in advance).
Now your format is planned. From there, it's a good debate how much planning needs done. I'd gets some books (try
Amazon, get them cheap, or even last years used). The books we always have: The Passporter, which is not only a touring and information guide, but a planner (we keep all our PS and agenda info in there); The Hassle Free Disney; and the Unofficial Guide to Disney. The latter two have touring plans according to what you want to accomplish and who you're taking (young kids? old kids? no kids?). Also, the act of reading these books will familiarize you with "how Disney works," per se. It also gets you hopped up for the trip! Birnbaums, the "official" guide to Disney, is an excellent resource book, but know it's put out in conjunction with Disney. They're a little biased.
Spend a lot of time here checking the forums (info coming and going all the time), and visit a variety of sites, including
www.mouseplanet.com and Deb's Unofficial Guide to Disney (
http://wdwig.com/). These are great sites for both solid information (when to go, what to do, where to stay, hotel and restaurant reviews, etc), plus breaking news. In particular, find trip reports on Mouseplanet and look at old reports from the time frame of your visit to learn what people did and saw during similar time frames. Also, go to
www.mousesavers.com, an incredible resource for finding discount information, e.g. how to get the best deal on cars, motels, etc. I'd join the Mousesaver's newsletter, which comes on the fifteenth of every month and often has info on inexpensive park tickets, etc.
That's how we've planned trips in the past, you'll get a hundred different views, but most will contain some similar components. I find a great way to save money leading up to the trip is to give up leisure time activity for a couple of months. Planning Disney is my leisure time activity. A well-planned trip is a successful trip, and the planning wets the appetite.
Hope all this helps!
Pat