Stacy Blackman, MBA Admissions Expert
It really varies by school. For many MBA programs, interviews are invitation-only. If you're applying to such a program, you should first focus on creating the strongest application materials possible in order to increase your odds of being invited to interview.
Other programs require that every single applicant interview either on campus or with an alum. If you apply to a program that requires interviews of all applicants, you'll still want to prioritize your application materials, as it's likely you will be asked to expound upon stories or accomplishments on your resume or in your essays.
Once you know you'll be interviewing, you'll probably want to start preparing a week or two before the big day. Research the school and see if you can find what types of questions are common, because as I mentioned above, it really varies drastically by school. But in general it's a good idea to have practiced (out loud) walking someone through your resume. It's also a good idea to have practiced telling a few different stories of times you lead a team or took initiative at work or handled criticism or disagreement. These types of "Tell me about a time when you..."/behavioral questions are very popular in MBA admissions interviews.
You'll also want to be sure you know whether or not your interviewer has read over your application. If they have, you'll want to try not to repeat the same exact stories you already told in your essays, and you'll want to be prepared for the interviewer to ask detailed questions about your background and accomplishments to date. They'll want to know WHY you went to the school you did, took the job you did, changed roles, got involved in a certain organization, etc.
However, if you're meeting with an alum who doesn't have access to your application materials, then everything you wrote about in your essays is still fair game for you to bring up.
Do your homework on the program you're interviewing for and be prepared to discuss why it's such a good fit for you, and that's half the battle!
Hope this was helpful, Stacy