In October 2010 i went for a day trip with my mum, we were there at the Park opening and went straight to queue for Big Thunder Mountain. It usually has a long queue so it's worth to try and go there first thing in the morning.
Another must do is Phantom Manor, another place that can have a long queue and so worth to be there early.
Same for Pirates of the Caribbean.
Peter Pan's flight, Mad Hutter's teacups in Fantasyland, Star Tour and Space Mountains if you like rollercoasters.
Around midday we changed to Walt Diseny World and had a look at the queues for Tower of Terror. As it was not too bad i queued for it (my mum waited outside and i was lucky enough because one lift had a spare sit and i was the only *lonely* one in the queue..) and then had some luch. After lunch we queued for Parachute Drops (long and slow queue) and then had a walk aorund. If you like rollercoasters both Nemo and Rock and Roller Coaster are a must do but Nemo can have long long queues.
Back to the main park for the Parade, tried to get on the Railway but we had to wait too long and so skipped it and went for a walk in the shops instead.
My advice is take it easy anyway, you can't go on every ride and see any show in one day so just have fun around and don't get stressed
