10. Know Every Detail in Advance
Where will you be staying? How do you get from there to a Disney park and back? Where will you be eating meals from? Which rides and shows are most important to you and/or your group? What FastPasses will be scheduled, and when?
These (and others) are the kinds of questions you should figure out the answers to before you get to WDW. Do your homework ahead of time and spare yourself the emotional burden of showing up and suddenly realizing there are so many details that suddenly need sorting out.