good luck man. i had many interviews. by far the most important thing is your grades. they already have an idea before you get to the interview if you were their first choice. they make interviews just to make sure you are not crazy. seriously. so just dress nice and be your self. and just think about a good question that you can ask the school.
if you have any more specific questions just ask.

Hey, I've applied for fall 2006 as well. Have you been to any interviews?

what's up man?
If it's just general advice you want, then make sure you're good looking. Dental schools, or at least the one's i've been to have this tendency to pick pretty people (provided they are equal on educational merrit that is). I may be overexagerating a bit, but when i see the med students, and the dental students there a significant difference in esthetics. Hardcore nerds goto med, cool nerds goto dental, I may by sligthly biased. So when you go for the interview..pimp yourself out. And make sure you have presence, and show a good sense of humor. You're going into a field in which patient-doctor interaction is impreative. Make sure you present yourself as an outgoing guy who can easily get along with others.

As far as the initial applications are concered....be smart, all the schools are tightening up on grades now. I know that Maryland has consistently raised it's criteria for the last couple of years. But if you get an interview, they know you're smart enough to deal with school, now you just have to show them your fun personality, and dedication to teeth.