When I bought my first 35mm camera, a pro photographer gave me some sage advice: Don't be afraid to burn up some film! For every 20-30 pics yoiu shoot, you might get one good one.
With the cheaper cost of digital photography, I can finally follow through on this advice. I shoot anything and everything - people, places, attractions, restaurants, shows, you name it. I tend to forget to take pics of my food, since I'm usually hungry when it arrives, but many others here do so before digging in.
Shoot anything that you want to remember. Got kids? Shoot their faces as you get on or off the plane, check in to your hotel, and enter the parks for the first time. Shoot your spouse, too. Don't just shoot posed pics (stand there and smile!), shoot pics as your family meets characters, talks to CMs, gets on the monorail, or stands in line for the bathroom.
I even take pics of my hotel room (before I mess it up, of course) and my rental car on each trip, just so I can remember what they looked like years later.
Photos are memories. Just shoot anything you want to remember.
And once every 2nd day (at the most!), go to one of the camera shops, located at the front of each theme park, and get your pics downloaded to CD. Cost is $12.99 per CD, limit 120 pics per CD, and wait times vary depending on how busy they are.
Off-site (if you have a car) you can get your pics downloaded to CD at any of the local Walgreens stores for $3.99 per CD, for as many pics as the CD will hold.