Who do you most admire?
This question really isn't so much about who you admire but why you admire someone. The interviewer wants to see what character traits you most value in other people.
What is your biggest weakness?
This is a common question, and it's always a tough one to answer. It can be dangerous to be too honest ("I put off all my papers until an hour before they are due"), but evasive answers that actually present a strength often won't satisfy the interviewer ("My greatest weakness is that I have too many interests and I work too hard"). Try to be honest here without damning yourself. The interviewer is trying to see how self-aware you are.
Tell me about your family.
When you interview for college, an easy question like this can help get the conversation rolling. Try to be specific in your description of your family. Identify some of their funny quirks or obsessions. In general, however, keep the representation positive -- you want to present yourself as a generous person, not someone who is hyper-critical.
What makes you special?
Or the interview might ask, "What makes you unique?" It's a more difficult question than it might at first appear. Playing a sport or getting good grades is something that many students do, so such accomplishments aren't necessarily "special" or "unique." Try to get beyond your accomplishments and think about what really makes you you.
What can our college offer you that another college can't?
This question is a little different than one asking why you want to go to a specific college. Do your research and look for the truly unique features of the college for which you are interviewing. Does it have unusual academic offerings? Does it have a distinctive first-year program? Are there co-curricular or internship opportunities that can't be found at other schools? The majority of college interviewers aren't looking to trick you or put you on the spot. The interview is a way for you and a representative from the college to get to know each other. The interview helps you and the college figure out if you're a good match. Try to relax and be yourself, and the interview should be a pleasant experience.