If there is a popular conception of the school (Princeton is isolated, Dartmouth has too many fraternities, Harvard has too little student-teacher contact), don't ask about it. Your interviewer will have heard the same question ten billion times. Save this question for your tour guide or for other students you meet while on campus. You don't want to seem off the wall by asking bizarre questions; but even more you don't want to sound exactly like every other boring kid who was in there before you. Challenge yourself to come up with creative and interesting questions and ones that you are curious about the answer.
Before the actual interview, practice. Many of you have probably never been formally interviewed. OK, maybe there was that interview to work at the Gap over the holidays, but did they really ask you questions that made you think about yourself and your future? Sit down with one of your parents, a teacher, or a friend (who can do this without cracking up), and have him or her ask you real, thought-provoking questions. Then answer them honestly and seriously. Allow your "interviewer" to critique you and listen to what he or she has to say. Maybe he or she will point out that every other word you used in your response was "like": "Yes, like, I really thought that this campus, like, was beautiful. It reminded me, like, of the Italian countryside, like, I went there on vacation this summer."
This practice interview is a great way to become aware of little things that you might not have even realized you were doing wrong. It will also get you started thinking about your answers and how you'll feel during the real thing.