I usually book about 1 week to 1 day out and just go to guest services and ask what they have at a certain park at a given time and there is almost always something, just depending on how picky you are about specific restaurants. We got Coral Reef and Trails end the day of last trip. So three months out you should be able to get most things if you are flexible on time. Also, if you do early dinners (as opposed to super late) there are more openings (4-5 instead of 6-8) and you can have a late breakfast/early lunch and save a meal a day.
Jan '07 Pop Century, Mar '07 Day Trip, April '07 Off Property, May '07 OKW, July '07 POR, Oct '07 Pop Century (& MNSSHP!!!), Dec '07 Day Trip
Jan '08 POR
Feb '08 Pop
Mar '08 Off Property
April '08 AS Sports - I think - still gotta book it