It's easy to write about what you *should* do... but what about things you shouldn't? Is there a short list of faux-pas that will instantly flag you as not being Harvard material?
The simple (and hopefully comforting) answer is no. There's no single thing you can do that would make an interviewer write you off. BUT there are lots of little things that may not add up in your favor.
(Most) interviewers are not trying to trap you. In the instructions we are given, we are in fact asked to think of ourselves as advocates for the students, and to take a personal and vested interest in them. So, you shouldn't get someone asking you complicated math questions or testing you on current events.
But you will be evaluated not just on the content of what you say, but your general maturity - how you present yourself, how well you interact with others, and how professionally you behave during the interview. These are places where you don't want to lose points.
So, without further ado, top ten mistakes.
1. Don't make it hard for the interviewer to schedule with you. Your Harvard interviewer is a volunteer. (And as far as I know, interviewers for most other colleges are generally volunteers too.) This is NOT their job. They often have jobs and families... what they don't have is a lot of time. When your interviewer calls or emails, respond promptly and make yourself available. A school club meeting, dance lesson, or tutoring session is not a good reason to reschedule an interview.
2. Don't ask your interviewer if he can meet you in another location. Even if you have a long drive. If you really want to attend College X, you'll find a way to make the trip.
3. Don't be late. Better yet be early. 10-15 minutes ahead of schedule is perfect. [You would think this would be obvious, but you'd be surprised...]
4. Don't forget that pre-interview contact is part of the interview. It is the first impression your interviewer will have of you. Respond to emails promptly. Use punctuation and write in complete sentences. Be on "interview behavior" even if you're just on the phone scheduling a time.
5. Don't forget any materials the interviewer has asked you to bring. Usually, this shouldn't be much more than a resume.
6. Don't forget to use your resources to help you prepare. Many students have parents who are professionals, who in their careers have interviewed dozens of people for all sorts of positions. They've also gone to dozens of interviews themselves. College interviews and job interviews have a lot in common. Have your parents do mock interviews for you. Ask them to give you their best interview advice.
7. Don't hold back. Pretend you're talking to a friend. Be enthusiastic, be excited. And of course be yourself. I've had interviews (not many, thankfully) that have been like pulling teeth. The student looks fabulous on paper but is very shy and clams up during the interview. Your interviewer is looking for a reason to be on your side... give it to her.
8. Don't put yourself down. Ever. You won't sound conceited, I promise. Remember, your job is to tell the best story possible with the data that you have. Do you know why you shouldn't put yourself down? Because there's a chance that your interviewer might believe you.
9. Don't forget to be interested in the interviewer. I wrote a much longer post on this earlier, but it's worth mentioning again here. Have a conversation with your interviewer.
10. Don't forget to follow up. Say thank you - then stay in touch afterwards too. Whether you get accepted or not, your interviewer is a valuable resource. Don't waste the opportunity.