I agree with the tip to smile. I was just there, and saw too many people that did not realize this was the happiest place on earth.
As for my addition, look for hidden mickeys! My wife & I got the book, and this was a great way to past the time. Many of the mickeys are in the waiting lines, and that made for a great time killer.
A couple of times, cast members would ask to look at the book, and they were amazed at some of the mickey locations (especially since most of the ones they looked at were at the places they worked).
Some of the mickeys are easy to spot, others you really need to keep your eyes opened, but either way, it made our trip more enjoyable.