Congrats on your interview!
As someone who has gone through couple of UMDNJ-SOM interviews, this is my advice:
RELAX as much as possible. I know this is easier said than done, but the interview is supposed to be as stress-free as possible. The admissions office staff is super cool and will make you feel at ease the moment you walk in. Be good to them!
Be friendly, smile alot, don't talk too fast, and make eye contact with BOTH interviewers. This assures them that you're personable and able to communicate well with others.
Have a good answer prepared for questions such as "Why osteopathic medicine?" or "Why do you want to be a doctor?". Name specific examples/experiences so your answer is not "generic".
Try to ask unique and thoughtful questions that show you have done some research on this school and that you're highly interested. The question time was the highlight of both of my interviews. During both of my interviews, I felt that we spent more time discussing my questions than their questions. I wonder if I scored really high on my interviews because of the question time.
Good luck!