Walt Disney World offers so much, you will never get everything done, whether staying three or thirteen days, so the most important thing to do is pick your favorites and start there.
Use
www.disneyworld.com or a travel book to review the numerous shows, attractions and parks on property. Decide which park(s) are most important to you. Magic Kingdom offers the largest number of actual attractions and could easily fill a whole day. If animals are your thing, be sure to choose Animal Kingdom. This unique park offers an up close view of a number of animals. If your family enjoys a look into the world of entertainment, then Hollywood Studios is for you. Then of course, Epcot. Epcot is divided into two worlds, Future World and the World Showcase. Future World is all about innovation and tomorrow; the World Showcase offers a view into the cultures of many of the countries we share this planet with.
In three days, my choices would be a full day at Magic Kingdom, a full day at Epcot and a day at Hollywood Studios. Unless you choose to stay for the night show Fantasmic at Hollywood Studios, you can often accomplish most of this park in less then a full day, so another option would be to head over to Animal Kingdom early that morning for a few hours, and then on to Hollywood Studios for the afternoon and evening. If you are staying at a Disney resort and have the park hopper option, you may want to consider taking advantage of Extra Magic Hours in the morning and evening and moving from park to park. These few extra hours will offer you a great opportunity to squeeze in a couple more things before your trip is up.
If you have added your passes to your resort stay package, you will need to stop there first and check in to pick up your park passes. If your pass is separate you can head right to the park and visit the ticket window to exchange your voucher.
Have a magical time!