Wow!!! Only 12 days!!!!
I stayed up really, really late

(ok I didn't even go to bed) Friday night looking through all the stuff that "Disney doesn't tell you" thread. Soooo much information. The most repetitive info was...
Bring a lot of one dollar bills for tipping, cab rides, etc.
Leave a pillowcase, picture frame mat, or autograph book at guest services with sharpies or fabric markers for character signatures-be sure to leave a bag of candy for them as a thank you.
If you are in an inside room, turn the TV to either the basketball court or bridge with the sound off before bed

and you will wake to sunshine.
Room Service: order cookies and milk to take to the movies or to have before bed, order coffee for the next morning (it stays warm enough), order the fruit & cheese platter to have as an appetizer before dinner.
On disembarkation day if you have the early breakfast, go to the Topsider buffet instead so you don't have to go super early.
Request a wake-up call and when it comes through, put it on speaker and everyone will wake up to Mickey.
Things to bring: an alarm clock with illuminated hands, a collapsible cooler, baggies (use for lots of things including ice in the cooler for easy clean up.), candy/snacks

(for tipping non-cash crew and to take into the movies - apparently snacks of this sort are expensive), over-the-door shoe hanger for all sorts of stuff, flashlight-the rooms can be dark, small fan, an old hotel card key to leave in the slider that turns lights on & off so you don't forget your Key To The World in the room, zipties to secure your FE and other things, scissors, and much more, but these were the ones continuely repeated.
You can order Mickey Bars at any of the restaurants for dessert or through room service even though they aren't on the menu.
Free pastries at Cove Cafe and someone mentioned they have the best coffee.
Order your drink from the bar instead of taking one from the server walking the pool with a drink tray...the bar drink won't have melting ice.
Fill out the surveys and write in the cast/crew's name. They receive lots of kudos that way.
Personal business cards (calling cards) to give to people you want to keep in touch with after the cruise.
Buy cheap Disney pins for trading on board (make sure they are Disney and not a knock-off.)
Bring OTC meds and small 1st aid kit.
Well, that's the list of "most repeated" tips that I found. I'm sure there are others. Please list them if you know of any more.
Oh...one more item...

if you are traveling with children and you are the only parent/guardian, you will need a notorized statement that allows you to take them out of the country. I think that one is actually on the Disney website.