Epcot is huge. It's basically two parks combined. The Sprawling hub and spoke modeled Future World, and the World Showcase wrapped around a lagoon can be daunting. These guidelines simplify the experience and maximize your time. They're all you need to know to get the most out of Epcot in just one day.
Budget your time
Epcot's Future World opens at 9:00. World Showcase opens at 11:00. The park usually closes at 9:00, but be aware of Extra Magic Hours if you are a Disney Resort guest and schedule your Epcot park day accordingly to get an extra two hours.
Get there early, plan to deal with long security lines and be prepared for baggage checks and screenings. Plan to spend about 90 minutes in future world and start heading down toward the World Showcase as it prepares to open.
Plan to spend a minimum of six hours in World Showcase before returning to finish the night in Future World.
Use the layout
Start on the left and hop in line for Test Track, followed by Mission Space if you are so inclined. I always ride it at least twice. It's my favorite attraction in the park, but it can make people sick and unfortunately (or fortunately, if you like short weight times) it is not a crowd pleaser.
If you have time and the wait is under 30 minutes for Spaceship Earth, get in line, but get to World Showcase by 11:00.
Go clockwise around the lagoon and don't backtrack. Mexico, Norway, America, France and Canada are the only five out of eleven World Showcase Pavilions with attractions. Most are continuously running shows between 15 and 30 minutes in length. Mexico has a 7 minute boat ride, and Norway has Frozen, which will eat up a lot of your time in the queue unless you have Fastpass. The ride itself is only 5 minutes long.
Some Pavilions like Germany, Morocco, Italy and Japan can be experienced very quickly unless you plan to stop for a large meal. They mostly feature just food and shopping. You can explore and enjoy each one at your own pace. It should take a minimum of six hours to complete the loop and head back to experience Future World West which has the final three pavilions.
Uses Fastpasses...or don't
Attractions you should use Fastpass for based on usual wait times are Test Track, Frozen, and Soarin'. but you will have to choose between them and you won't be able to secure another one until the first is used. Since Fastpass dictates the times you can experience the attractions, you should adjust your timing to fit. If you have a Frozen Fastpass for 1:00 you should stay in Future World until around 12:00 instead of 11:00. You may come across a short standby line when your Fastpass time isn't up yet. If this happens, take the standby.
Only Eat at quick service
There are some good table service restaurants in Epcot. A couple of them are flat out amazing, but dining in a restaurant can be a major time killer. In order to maximize time and increase the potential food stops in different locations, only dine at quick service restaurants. This is a great way to get the most out of different kinds of cuisine and experience more of all the pavilions in a short period of time.
Follow these simple guidelines and you will cover a lot of ground. There is so much detail in Epcot that there is always something new to discover. But if you have only one day to squeeze it in, this is how to see and do as much of the park as possible.