Easy Disney Dining Reservations: PSCalculator
If you are planning a trip to Disney and MUST have reservations (or priority seating in Disney-speak) for some of the popular character meals (like Cinderella's Royal Table), use this website! PSCalculator.net helps you calculate the exact day you can call and make your reservations for each type of meal. Some events / restaurants allow reservations to be made up to 365 days in advance - most are 180 days in advance. (Yes, 6 months!) We used the tricks in the Unofficial Guide to Walt Disney World and this calculator to obtain lunch reservations at Cinderella's Royal Table during a relatively busy time of the year. If you're planning a Disney trip, check out this website so you can plan your reservations early enough!
FYI - just keep in mind that a reservation is not exactly what you think when you normally have a reservation. When they say priority seating that is what they mean. If you have a time booked - say 6:00 - it could be anywhere from 6-7 before you are seated. It takes longer the more people you have in your party.