My best advice is to buy (or get from your local library) a copy of the Unofficial Guide to Disney World. I think people have hesitated to respond to your post simply because there's so much information to try and convey that it's overwhelming -- plus, not having details about your party (size, ages) and arrangements (where you're staying, where you want to dine, whether you want to do character meet and greets in addition to rides and shows, etc.) that it's hard to customize an answer.
In general, the best tip for any WDW visitor -- especially during busy times of year -- is to arrive early (well before the park opens, so you're among the first in when the gates open), and with a smart touring itinerary (e.g., headliner attractions first - unless you have a fastpass for it later). The top-priority attractions will be different for each park and depending on your party's individual tastes. My personal advice to make your visit as stress-free as possible is to break up your touring into manageable chunks, especially if you're like me and get stressed out by noise and crowds after awhile. Go to a park at rope drop, tour until lunch (at which point the crowds will be peaking), and then head back to your hotel for naps or a swim. Go back to a park in the evening and tour for another 3-4 hours or so.
If you do borrow or invest in the Unofficial Guide, I also highly recommend subscribing to the touringplans.com website (run by the Unofficial Guide folks -- there's a subscription discount for those who have the book, but it's inexpensive either way). It will provide you with sample touring plans, and allow you to customize those -- or create your own from scratch -- which can be optimized for your travel dates, taking into account the crowd levels that are expected.
