1.  Arrive on time (early if possible)
2.  Learn a little about the play that you are auditioning for.
3.  Act!  Don't just read.
4.  Slow down and enunciate.
5.  Don't fidget or squirm
6.  Dress comfortable but not sloppy.
7.  Do not make excuses and do not apologize.
8.  Bring something to write with and write on.
9.  Be aware of what is going on - do not be distracting.
10.  Follow the 4 P's:  Be Prepared.  Be Polite!  Be Prompt!  Be Professional!

And remember - auditions START the moment you arrive not just when you are called upon to act.