All in all, what would you say is the biggest mistake most first-timers make on their Disney vacation? A co-worker is planning on going to WDW and I'm trying to help her make the most of it.

I think the most commmon mistake is not familiarizing oneself with the parks ahead of time. (I gave her a used copy of Birnbaum's from a few years back.) They go in, are overwhelmed by all the new sights and sounds, and never realize the wide variety of options they have. (She's making Cinderella reservations because someone told her "you HAVE to do that!"--when I asked if her two boys wouldn't rather have a meal with different characters, she said, "they have other ones?")

Anyway, just wanted to see what you all had to say on the subject. Thanks for your opinions!