Hi,
Prepare for good "honest answer" on your weaknesses (ie...MCAT, GPA, extra activities, research...). Be confident and have fun with them. My interview is funny in that none is smiling except me. They asked me to tell them all about what I did since middle school. I answered them back and forth like crazy; then I asked them if I could get out for couple seconds to drink water. I told them that I forgot my "saliva substitute" home, and I finally got them to smile with me toward the end. To my surprise, I was accepted 1 week later.
Good luck, man.
😎