Hi Erica - Epcot is one of my all-time favorite parks, so it's a great choice. I definitely have some personal favorites to recommend, but I also suggest you check out the
Epcot section of the Walt Disney World website to make sure you see all of the attractions available.
When you arrive at the park, I'd recommend you ride Test Track and Soarin' before the lines get long (you may want to grab a FastPast for one while you ride the other). While at the Land Pavilion checking out Soarin', consider riding Living with the Land if the line isn't too long. It's one of my all time favorites. Next, check out Ellen's Energy Adventure. Once you are done there, head to the World Showcase if it's open (the World Showcase often opens several hours after Future World).
The World Showcase is my favorite place to stroll and enjoy. There are great treats and drinks available at just about every country, and several of them have rides and/or movies. Grab lunch at the World Showcase, either at a table service restaurant or a counter service restaurant, and relax.
Looking for souvenirs/Disney merchandise? Mouse Gear in Future World is my favorite shop at Walt Disney World!
Towards the end of the day, visit Spaceship Earth. Since it's the first attraction as you enter the park through the main entrance, it's typically busier at the beginning of the day, but slows down toward the end of the day.
Most importantly, have fun!