Find an agent who is experienced with Disney auditions and ask them to look for upcoming Disney auditions. Many Disney recruiters often visit lower tier parks to scout for great acting talent. Always work the audience after shows to hear about Disney contacts.
If you are a college student, start with the College Program. From there, you can make sure you like the company and get your foot in the door. Otherwise, just go to Casting in Orlando and make an appointment to audition.
