1. Invest in the best pair of walking shoes they make and break them in ahead of time. Dead serious here. I wore some $60 Nike shoes one year and my feet were throbbing by day 3.
2. Go in the fall, anytime in October. Cooler temps, much cheaper airfare (fly Allegiant, direct flight) smaller crowds, kind of (it's ALWAYS crowded), great Halloween/fall decorations throughout the park.
3. Staying for the fireworks is an absolute must. My favorite part of the entire experience. They do an amazing light show/story coordinated with fireworks.
4. Plan a side trip to Clearwater Beach as an off day from theme parks. Take a boatride to watch the dolphins on the ocean.
5. If you love thrill rides, Harry Potter, or Marvel, you will actually enjoy Universal Studios better. Beware though, it's EXPENSIVE
6. It seems like there is a rainshower there at least once per day. Be prepared for that. It's usually just a short-lived pop-up shower, but we've been there around 10 times and have gotten rained on about 5 of them.