Maybe some of my tips will be repeats, but never hurts to hear it twice, right!
1) Bring bathing suit in carry on-- so you don't have to wait for your bags to be delivered to your room!
2) Bring extra film, and a waterproof camera. I recommend using disposibles, so you don't have to worry about camera malfunctions. Bring your camera EVERYWHERE!
3) Skip the lunch buffet at least once, and eat at Tritons/Lumiere's
4) Bring an address book, and meet new people! Exchange emails addresses with people (especially tablemates, and you can stay in touch, swap pictures and stories!
5) Bring thank you cards for the staff. Coming from a cast member, it's the little things that keep the pixie dust in your heart alive!
6) Unless you can't live without soda 24/7 DON'T DO THE SODA MUG DEAL. You can get soda for free at every sit-down meal, I always got them at dinner, and even at the sit-down lunch at Tritons. You only need to pay for soda at bars and at poolside really. Besides, when you are swimming and in the sun, it's better to drink juice and water anyway!
7) Save everything, and make a scrapbook.
8) Go to at least one program/activity a day. The cruise staff is great, and you get to meet people other then the ones you see at meals.
9) Play, or at least attend Jackpot bingo the last night. It's a blast. WARNING WARNING WARNING BINGO IS HIGHLY ADDICTIVE, but FUN FUN FUN!!
10) Remember Hakuna Matata... everyone wants a perfect vacation, but nothing can be absolutely perfect. Just remember, you are safe, with your family and friends, sitting on a gorgeous ship, basking in the sun. The cruise staff works EXTREMELY hard, from your servers, to your stateroom host, to the person putting towels next to the pool. They come from countries, where often times, a doctor's visit, and even clean water is unheard of. You are blessed! Enjoy every minute, it's a lifetime opportunity, so make it a lasting memory!