Get your lines if you have any.
Always have headshot and resume.
Dont Worry about the competition.
Dress the part.
Be in a good Mood.
Dont goof off, concentrate.
Dont flirt with the Casting Director.
Remember to warm up vocally,emotionally,physically, and mentally.
Be nice to your competition. You never know who you may end up working with.
If possible go to the location of the audition the day before. IF you have that much notice. We all know that sometimes you arent that lucky. BUT if you are, going the day before at the same time you should on the day of the audition tells you where it is, the traffic pattern, and parking. Lets face the facts here, parking can be a bitch when you go to a studio.
Go in wadrobe.
Dont chew gum while auditioning.