Here's how we have done each:
MK - travel down Main Street and hang a left towards Adventureland. We start there and hit all the rides/shows we want moving in a clockwise motion.
Epcot - this one is a bit tougher and we end up doing some back tracking or doing 2 days at this park. Start with Spaceship Earth, go to the Land Pavillion, then to Imagination Pavillion. If the park has been empty we then backtrack to the Cool Zone to and head across to Ellen's Universe of Energy. From there we start the lands in World Showcase in Mexico and walking clockwise to England.
HS - Got to Sunset BLVD and do TOT and RRRC. After that everything else is slow paced.
AK - Start at Dinoland and work the rest of the park counter-clockwise.