Read the play. If you are auditioning for a specific play, many of the director's questions will focus on your knowledge of that play. If you are preparing for a general audition, the auditor's questions will be more focused on you. Actors typically perform a monologue at a general audition, which is meant to introduce talent to a theater that it can use for an entire season of shows. In this case, it is wise to be familiar with all the published plays the theater is producing that season.
Write your own interview questions. Think like an auditor and come up with a short list of questions. A director wants to know what type of artist she will be working with for the next few months, so prepare for questions that ask for your personal opinion. Three or four open-ended questions will suffice because auditions usually last less than five minutes, so an auditor won't have time for more.
Ask a friend to interview you using your questions. This gives you a chance to answer questions out loud. Ask her to give you feedback about your body language and voice. Your physicality will reveal a lack of confidence long before your words, so be wary of awkward gestural language.
Relax, relax , relax. Where an audition is asking you to define a character, an interview asks you to be yourself. Use relaxation techniques to center yourself before walking into the audition room. A few deep breaths or a few minutes of meditation go a long way.