If the crowd level is expected to be high, they will have FP working that early.
Arrive 1/2 hour before opening. IF you want to do Fantasyland, go there first. Get FP for Pooh or Peter Pan, ride Dumbo, PP or Pooh (whichever you didn't get the FP for), the FP next, Small World, Philharmagic, Carousel, Teacups.
If you don't want to do Fantasyland, go to Tomorrowland and do Buzz, Indy, Space Mountain - then head to Splash and BTMR.
This is just what we did in March, really nothing scientific, but it worked great for us!