1) The obvious, look at the feedback section on here. However, don't memorize answers or just assume those are the same questions you will be asked. It gives you a feel for how interview day might be and maybe a style of questions. Remember, these are user submitted. Take what you see accordingly. Also, pay attention to when these were submitted. Schools change (e.g. ASDOH no longer ask current events or geography questions).
2) Mock interview. If your pre-health department offers something, use it. If not, try to practice with someone who might be able to give halfway decent feedback (dental students, people who have conducted interviews before, preferably in an academic setting). Best friends, significant others, and parents aren't great. If you're feeling up to it, video yourself. I realize some of you are just so smooth that this notion is ridiculous. But for the rest, you'd be surprised how much distracting, weird stuff you do. "Um" and "uh" and "you know" and all the fidgeting. If you can't find someone to give you a practice interview, at least practice the main questions out loud. Not rehearsed. But you should be able to explain why you want to be a dentist clearly and concisely. Sure, it sounds good in your head and when you write it in your statement. You know what you mean, but it might sound a little incoherent coming out of your mouth if you haven't told the tale recently. Webcam that bad boy if you want...and then delete it before someone gets a hold of it. Two of my mock interviews from pre-dent days were recorded. So embarrassing, but it was the best feedback on how much I suck(ed?).
3) If you haven't interviewed in a while (or ever, for some of you), pull up a list of generic interview questions. These don't necessarily need to be from dental or med school interviews. Your biggest weakness. Challenges you've overcome. Stuff like that. Don't spend too much time on them (a minute max...just make it toilet material or something). Just read through them and think about how you might at least start answering them. If they happen to come up, you have something to draw on instead of a blank. That's why dark suits are best....you can wet yourself all through the interview without anyone noticing when they catch you off guard with "what fruit would you be?" You're just packing some ammo just in case they come up. For the "tell me about a time" or "give me an example when" questions, it's nice to be able to draw on a decent experience instead of the most random one that pops up in your head. When they asked me what was the last book I read, I was glad I had come across that earlier and put some thought into it because "a textbook" isn't funny.
4) Know your schools! Whether you have 10 interviews or 1, treat that school as your number 1. Learn what you can before you get there. You may even find that you actually like the school if you just applied on a whim because their average accepted stats looked good to you. The more you look into things, you might actually come up with some legit questions to ask at the interview. That helps show you actually do know more than what's on the school's website and that you have put some thought into what's important to you in a program. If you can get access to students, do that. If you look around here enough, you can probably get access to someone from just about every program out there. Whether they're nice or even responsive is another thing. But it's worth trying. Last thing, attempt to locate school newsletters or alumni quarterly magazines things or similar things. It can serve as a tiny peek under the hood and have some info not found elsewhere. Get creative with google and you'll find some fun stuff.
5) Take the trite advice from those who came before you: relax and be yourself. When you're getting hammered in the sciences your first year and you see the little pack of interviewees coming around, you're going to look back and realize how neurotic and strung out you were during interview season and how you probably acted like an uptight tool at your interviews for no reason. You may even be ashamed at how much time and energy you spent on just your attire (my favorite threads on here). This is an important step in your life and shouldn't be taken too lightly, but take the stick out when you walk into the interview and show them you.