The interview will feel very relaxed, so there's nothing you should feel anxious about.
Read top interview questions threads on SDN and think about it in your head and see if you can come up with answers for those.
For me, a lot of questions from top interview questions threads were pretty accurate. Or I should say the interview questions were pretty generic, so those GENERIC threads were pretty helpful.
http://forums.studentdoctor.net/threads/top-10-interview-questions.669600/
Leave about 30 minutes before the indicated time, otherwise you will be waiting for too long(whole bunch of people were waiting in their car because they got there too early). I left almost 40 minutes before the time and it didn't take me long at all to get there and the parking lot is right in front of the building, so there's no time wasted there as well.
Is your interview on Saturday? If so, you and other applicants will be divided into four groups, according to your last names.
If your last name is around A-L, you will probably be in first or second group to be interviewed, otherwise, you will be third or fourth.
I personally really liked the fact I was the second group to interview. I wouldn't have minded first turn either.
Third and fourth, you will be anxious to get your interview over with while you are touring and doing Q&A session
Just relax and have fun.
Take some pics of the clinic too. It's nice!
Don't forget to look nice as well