Your Interview Goal. It's three-fold:
Show fit. In the words of the Wharton Adcom Blog, "The interviewer is assessing your fit for the Wharton MBA program." Think of your professional and educational background and needs and the school's methodology, strengths, and career opportunities. Realize, however, that the interview is not just about you as a professional: it is also about you as an individual and human being.
Inform the school about recent accomplishment and achievements. Did you retake the GMAT? Earn an A in calculus? Get a promotion? Take on a leadership role in a new project? Try to include inform your interviewer of any new attainments in your interview. Doing so will strengthen your profile overall and portray you as a growing, dynamic individual
Demonstrate your communications and interpersonal skills. The latter is important for all, but critical if English is your second language and/or your transcript and test scores lead one to question your communications skills.
MBA Interview Tip #1: Enter the interview with SID:
Show you are a match with the program.
Inform the interviewer of recent accomplishments,
Demonstrate your interpersonal skills.
MBA Admissions Interview Must-Know #2: You
You. You are the first topic you need to know. After all, the interview will be about you. What do you want to do after your MBA? Why do you want to attend this program? When have you demonstrated the qualities this school appreciates, the qualities that will show you belong here? Much of this information appears in your essays or was uncovered in the preparation and introspection that took place before you drafted your essays. (Did you jot down notes? Keep a journal? Use them.)
In her recent BW interview, Dawna Clark, Director of Admissions at Tuck, gave the following very concrete advice to applicants facing a "blind" interview, which at Tuck and many other programs means the interviewer only sees your resume.
"I would recommend that people approach their interview with a strategy. When candidates are applying to Tuck, so many of them are so bright and so impressive, and there are probably 50 things that they would love to talk to us about in their interview. But there's limited time, and I would recommend that they spend some time thinking about five of the top skills, experiences, or accomplishments that they most want to emphasize.
"I would literally write a list of everything that you're proud of before your interview and then cut it in half, and cut it in half again and cut it in half again, until you say, 'You know what? If I have limited time, here are the five points I'm really hoping to get across in this interview.' With each of those five bullet points come up with some examples and substantiate them."
Dawna provides excellent suggestions for an interview strategy where you will truly be prepared to present yourself.
MBA Interview Tip #2: Know the few most important things you are proud of and be prepared to discuss them.
MBA Admissions Interview Must-Know #3: The School
The School. What does the school value and emphasize? Innovation? Leadership? Teamwork? Yes, I know all schools value all these qualities, but some emphasize one more than another. You need to understand those differences. How do they define the qualities they value?
Note the effort that Haas devotes to clarifying what it values when it says Leadership through Innovation. At its presentations, on its web site, and in the recent Accepted.com chat, Leadership Through Innovation has become a major focus. First understand what the school values and then prepare to explain why and how you share those values.
How does the program work? Cohorts? Learning teams? 
rojects, lectures, cases? 
lan to answer questions in a way that demonstrates your knowledge of the program and prepare a few questions that show you have done your homework Let your questions and answers reveal that you have thought deeply about the program and how it meets your educational needs and will help you achieve your professional goals, while also recognizing opportunities for you to contribute and pursue your non-professional interests.
Again, drawing on BW's interview with Dawna Clarke, Tuck's Admissions Director, who advises:
"Another piece of advice is to do research on the school. A lot of schools will talk about the fact that they're looking for fit, and basically what that means is that they're looking for people who've done their research and are going about this decision using some insight and good judgment about what it is that they're looking for and what that school has to offer. There are so many good schools out there, and what you want to do is convince your interviewer or your admissions committee that that school is a good bridge between your past and your future plans.
"The best way to make a compelling case is to really show that you've done your research and that you know what the school has to offer and what you have to offer the school."
MBA Interview Tip #3: Know what the school values and be ready to show that you share those values.
MBA Admissions Interview Must Know #4: The Interview Type
The Interview Type. Is it blind (where the interviewer knows only what's on your resume and what you tell him or her)? Or is it informed with an interviewer who has gone thoroughly through your file (for example, HBS or MIT). Is it a case presentation (LBS or IMD)?
If blind, then you can use material from your application because that material presents your most impressive experiences, and it will be new to your interviewer, but don't limit yourself to that material.
If you are interviewed by someone who has gone through your file, prepare to address weaknesses and gaps and also be ready to bring something new to the interviewer's understanding of you. Know how to go deeper into the stories you have told and prepare to tell additional anecdotes.
Whether blind or informed, make sure to tell your interviewer of important developments that have occurred since you submitted your application - a better GMAT score, an A in a business-related course, a promotion, leadership of a community service initiative... This last step is particularly important if you are interviewing at schools like Harvard and Wharton, which in the past have discouraged or not accepted new information from applicants after the application submission date -- even if the information is highly relevant and/or the applicant has sat on the waitlist for months.
MBA Interview Tip #4: Know the type of interview you will have and prepare accordingly.
MBA Admissions Interview Nice-To-Know: Your Interviewer
In the words of a Columbia applicant who recently submitted a report to the MBA Interview Feedback Database:
Was there something you wish you had known ahead of time?:
Yes - I wish I had known more about the interviewer: what company she worked for, her role in the organization, her seniority, etc. That would have helped me mentally prepare for the kind of person I would be speaking to and be able to relate to her better.
If you have your interviewer's name, google him or her and try to glean a little information about this person so you can connect better on an interpersonal level. If you don't know your interviewer's name or simply can't find it on the Internet, don't sweat it. It isn't a must.