Today at the Unofficial Disney World we say make the most efficient use of your time while at Disney World. The best way is to be there at rope drop. What is rope drop? Thats what Disney calls the opening of the park. So if the park opens at 9am be there about 15 minutes early.
Here at the Unofficial Disney World we say the early bird gets the worm. In other words the parks are almost empty the first few hours of the day. Plan before you arrive which attractions you wish to ride and go to them first thing. You might have a 5-10 minute wait, but a couple hours later you will have a 45-75 minute wait at the same rides if they are some of the most popular.
If you are staying at one of the Walt Disney World ( WDW ) Resort hotels look into Extra Magic Hours (EMH). Each day 1 of the parks will open an hour early or stay open a few hours later. This is a great benefit for hotel guests for more time in the parks and shorter lines.