Have your school just said that their next school play is Alice in Wonderland Jr. If so, keep reading.

[edit] Steps

Know what song you are going to sing, and no matter what, (unless you have to) do not sing a song from the play. If you do, then the directer might only see you as that part.
A perfect song for your audition is Thoroughly Modern Millie.
Now decide on 2-3 characters you would like to be. A good thing about Alice in Wonderland is that most parts (even the Mad Hatter) can be done by a girl or a boy. If you can't find the scripts, then go to http://www.broadwayjr.com/audition/default.asp and click on the Alice in Wonderland Jr. icon. Next click on the character(s)you would like to audition for. If you have no idea who to audition for, consider choosing one of the following:
An Alice (depending on your height)
1 non singing role (Cheshire Cat, Matilda, King of Hearts)
2 wacky wonderland creatures
and, if you are a girl, a flower. A lot of very talented girls think they are too good to be a flower, but the theatre world is not fair, so you should always audition for a small part too.
Start practicing at least three weeks before your audition; you should be practicing your song as early as possible.
Remember to practice your lines as well as your song, because Alice in Wonderland Jr. has a lot of speaking parts.

[edit] Tips

The best song choices tend to come from musicals. Avoid rap and overly simple songs like Twinkle, Twinkle Little Star.
Always smile.
Walk with a spring in your step, because Alice in Wonderland Jr. is a perky musical.
Do not limit your self to leads, because it will be boring being the nice sweet lead while everyone else is going crazy.
Keep your height in mind (if you are 4 feet you will probably not get the tall Alice part).
Have fun.

If you don't get into drama club, use this year as a time to practice.
Change all of your nervousness into energy.
Do not brag that you are going Alice or any other part, because if you don't get the part people are never going to let you live it down