First time? aw that's great! But anyways try to hit the parks as early as possible.
On that note, While in MK, if you get there really early you should try to hit the big attractions first. Such as, Splash Mountain, Space Mountain, Jungle Cruise, Pirates of the Carribean, Big Thunder Mountain Rail Road, etc etc.
Epcot: Soarin', Testrack, Mission Space
MGM: Rockin' Roller Coaster, Tower of Terror
AK: Dinosaur, Expedition Everest, Kaliminjaro Safari
After you do all those big attractions first you will then have time to eat, ride other rides, catch a few shows, and then possibly ride some of your favorite rides again. We always try to ride the more popular rides first in the early AM because that's when they have the shortest waiting time.
Ok hoped this helps! Have a wonderfull, fun and magic filled trip!
