you can prepare for your interview by starting to think up questions to ask people at the school (admissions personnel, professors, deans, students, etc.) now. If you come up with about 5 questions for every day between today and October, you just might have enough questions to ask one every time someone at the school asks you "Do you have any questions for me?"
Seriously. I ran out of questions after the first 10 minutes of the 4 hour long interview day.
But they know it too. The students and the staff all start making fun of themselves near the end for asking you if you have questions.