My best tip is to stay tuned on this forum! We cruised for the first time this past May and I read the Passporter, but I learned all the best tips from this board. Not to mention, it was great meeting the people I was chatting with for months!
The best things we found out prior to cruising were:
1. Bring a plain pillowcase and markers and drop them off in a ziploc bag at the Guest Services desk. All the characters will sign this at no cost and you have a wonderful souvineer for your kids (or adults)!
2. If you want to do something special for someon you love, use Shirley's Perfect Gift. She creates the best baskets.
3. Bring pirate gear! We had the best time dressing as pirates. It made the night so much fun!
4. Bring a travel size Downey Wrinkle Releaser spray to take your wrinkles out as you do not have an ironing board in the room (it is in the laundry room).
5. If you are bringing dress clothes (suit etc.) send it to down to be pressed/drycleaned the first day on board. It was cheaper than getting it done at home and I didn't have to iron any of dh's suits.
6. Read your navigator ever day to find Character appearances. They list the location and times. We read it every morning over coffee.
7. Speaking of coffee, I recommend ordering a pot of coffee right before you go to bed. They deliver it in a carafe and it stays hot til morning.
I'm sure I can think of a hundered more, but these are the things that come to mind...