Take dance or singing lessons (improve your odds by taking both). This is a huge plus for Disney roles.
Get headshots taken (these are photographs that you can later send out when applying to be on a Disney show).
Find an agent. Agents are important in helping you getting a role on the Disney Channel. By visiting the SAG (Screen Actors Guild) website you can find an agent for any state in the U.S.
Audition. You can find open auditions for the Disney channel all over the world by going to Disney's corporate website.