To
prepare an audition, ask your
self if you are auditioning for a school, or for a play, or for a very specific role. If you plan to go to a school, you should write yourself a list of which ones, and keep copies of the letters that you send to and receive from the
institutions.
It is standard to have at least two contemporary and two classical monologues, and perhaps a song or two.
The monologues should contrast each other in lines of comedy/tragedy or high/low energy.
You should research contemporary monologues in books, not on the internet, and you should be able to identify what play a monologue comes from (if from one it comes).
Your classical (read: Shakespeare) monologues should not be prose, and should not be "done to death" (To be or not to be).
Make your list of possible monologues, and highlight those that you will do for sure. Work on these. Make a list, too, of pieces that you would like to work on in case they ask for more, and be sure that you know these.