Practice talking "on camera" at home. If you don't have a camera with a playback, talk to your computer web cam or even a mirror. The goal is to be comfortable and natural in front of a camera.
Learn to talk with your face, not your hands. Practice emotions without overplaying the sadness, happiness or boredom you are trying to express.
Speak directly to the camera. Every audition is recorded so that the casting directors can review each performance when they are narrowing their selections.
Say your name at the beginning of the audition, when the casting director asks you to "slate." What she is asking for are your name, where you are from and what age range you can play. It is not necessary to state your actual age unless you are asked. If she needs further information, she'll ask.
Relax and let your personality show. Disney casting directors look for actors who can portray believable characters.
Perform whatever the casting director has asked you to do. If it is cold copy, you will have received that copy prior to the audition. It is not necessary to memorize the copy but to be comfortable with the words and the message. You may hold the cold copy in your hands as you audition. If you are asked to sing, sing eight bars. If you are asked to perform a monologue, this is a memorized speech you will have prepared before the audition. Be sure it is age appropriate. You don't want to perform a monologue a grown man would say if you are only 10 years old. You should receive instructions before your audition on the material you will be performing.
The casting director will conclude the audition by either asking questions, or by simply saying "thank you." Be sure to thank her for the opportunity and then leave quickly.
Move on. That is, do not waste time fretting about whether you will receive a call-back. Casting decisions sometimes take weeks, maybe months before the next step is taken.
Write a hand-written thank you note to the casting director and include an additional headshot/resume with that note to remind her of who you are. Make it short and sincere.