You pre-pay for a reservation on the Disney World website.
I have found it opened up for my January vacation around late November, so they must allow bookings to start a few months out.
Good luck! I can't wait to do it in January
"To all that come to this happy place: welcome...Here age relives fond memories of the past, and here youth may savor the challenge and promise of the future.."
Most Recent Trips:
September 2007 - Pop Century
September 2011 - Pop Century
January 2012 - Pop Century