I hate to push this on people because some folks just can't do this, but...
Plan your day in advance down to what rides you want to ride, shows you want to see, parades, and fireworks. Then plan a route around the park and use the fast passes every time you can.
Also, some general hints:
1) get there so that you are one of the first few hundred in the park. You will get on 5-10 rides in the first 90 minutes which is before most people even show up. By then you will already have two sets of fast passes.
2) eat lunch later in the day than you normally would. You will be eating when most people are riding and in shows. You may also want to eat just before the parade so that you can relax after eating. Same with dinner.
3) If you are park hopping, know that most popular fast passes are gone earlier in the day so you probably won't get any in the second park. Regarding park hopping: Epcot and Magic Kingdom take 1-2 full days each to see and do everything. Animal Kingdom can be done in less than a day, especially if the kids are older. Disney Studios is about a day. Hop from either Studios or Animal Kingdom to Magic Kingdom or Epcot and do some of the things you missed the first time.
4) You must see Fantasmic and the fireworks at Epcot. The ones at MK are good, but not as good as the others. The nighttime parade at MK is great though.
There are single rider lines on some of the attractions, but fast pass is the way to go.