1) Watch the indoor shows intermittently throughout the day.
2) Go to the rides with the longest lines early in the morning so you don't end waiting in them in the dreaded heat.
3) If you're starting to feel a little tired, sit down, relax, and drink water.
4) Bring a lot of bottled waters with you. That way, you don't have to walk and search for a water fountain. Don't forget to fill them at a water fountain when you come across one.
5) Get a towel wet at one of the water fountains and wrap it around your neck. This will help you keep cooler and last longer in the heat. This is a common practice in warehouse and construction environments.
6) Don't drink cokes. They can actually increase the probability of dehydration.
7) If you're feeling tired and exhausted, go back to the hotel. You're probably already dehydrated or getting close to it. Going indoors to see a show won't cut it. What you need is rest. Come back in the late afternoon or evening when things are cooler.
8) Spray fans are wonderful. Just make sure you don't them at the park. You can get them way cheaper at the average store.
9) If the line to a ride is extremely long, skip and come back at a later time. The ride isn't going anywhere.
10) Don't drink coffee.