There are two basic mistakes made by the students:
First, the Student is supposed to schedule the interview. When the student contacts the interviewer, they have to realize that the interviewer is a volunteer with lots of other commitments. The student should know by the start of senior year in high school which colleges she/he will be applying to and which ones require an interview. They should schedule that interview as early as possible. This past Fall, I conducted four interviews and each applicant contacted me on the last day possible (per the college’s web site). Two for Early Action and two for regular admission.
That will be noted in the interview report. If you can’t budget your schedule well when informed of deadlines at least six weeks in advance, then how can you budget an intensive college life?
Second, the applicant should come to the interview with two purposes in mind:
The ability to tell the interviewer what the applicant does other than study and other than academic subjects. That is what the interview is all about. The interviewer does not care about your grades, nor scores, nor how many AP classes you take. The interviewer wants to know what else you do. Fifty percent of the applicants to most top colleges could do the work and graduate in four years. However, the college can only accept one of every seven of that 50%. Where you distinguish yourself is in that interview.
Have questions to ask. The interviewer is there to answer questions about the college. In my case the interview should be conducted before you finish the online application. You may learn something from the interview that will guide you better in filling out the application.
The applicant’s appearance should be neat and appropriate, like for a job interview. However, a tie is not required for the male applicants.
In my case, it is (roughly) a 90 minute two-way discussion, and you should make the time fly through your conversational abilities.
Relax, and enjoy the interview process. The interviewer loves her/his college and loves to interview otherwise they would not being doing the interviews. Take advantage of that.
NOTE: I give “extra brownie points” to an applicant who has done her/his homework and looked up information on me, and works that into the interview. It shows initiative. After all, I was an undergraduate at that college and many of my avocations were cultivated there.