(1) The weather is often better in the morning than the afternoon. This holds true especially in the summertime. As the afternoon heat builds up, thunderstorms tend to form up. At theme parks, it could shut down rides as you are waiting in line for them. At the beach, it will obviously make you not want to stay there. Most of the time, the morning is a better time. Save this part of the day for outdoor thrill rides and beaches.
(2) Theme parks are expensive, and I am not just talking about the ticket to get in. You will have to pay for parking if you came in a car. Then, the food prices inside the parks are very high. Often, you have to go quite a ways from a park to find more reasonably priced food. There is nothing stopping you from bringing your own food in. Of course, the tradeoff is that you have to carry all of that stuff.
(3) The busiest times for the theme parks are school holidays such as Christmas/New Years and Spring Break. Of course, the summertime is busy. During busy times, it helps to get to the parks early and go after the big name rides right away while lines are still not so long.
(4) Research the internet extensively for hotel and theme park discounts. There are a vast number of sites that deal with travel to the Orlando area. Some of them are probably just a click away. I will bet that some VT sponsers dealing with the Orlando area make sure to have their links on any Orlando VT page (hint, hint). It is best to compare some sites and shop around. There are a lot of deals out there.

