Interviewers love quiet confidence.
Interviewers hate overbearing applicants.
Interviewers will reject overly humble applicants as lacking.
How do you walk the fine line between confident and overbearing, or even desperate?
The people who will interview you are pros. They have seen it all. They can tell the posers from the real thing. If you go in there and try to fluff them with fake bravado, you will look foolish. Rather than confident, you will seem annoying. Too much talk about "me, me, me" even can seem desperate. At best, you will get sympathy. At worst, they will never ever want to see you again.
It's worth remembering that most times people talk too fast, they come off as nervous and unimpressive. It's important that you find the balance.
So try this...
First, don't talk too fast. Too many students try to get in as much information about themselves in record time in order to impress the interviewer. This is one of the fist signs of desperation and it will doom you right from the start. Besides, you will bore the interviewer and they will start to tune out. You'll sound like a robot.
You really want to keep their attention, and nothing helps to do that like pausing for an occasional breath. Speak slowly and clearly. (And, of course, breath.)
Don't try to cram every little thing you've ever done into your interview. Get the important stuff in, but leave time to convey your personality. Unless it's a blind interview (one done without your application in front of them), they will already have the basic facts and figures of your background.
And don't tell the interviewer that you've dreamt of getting into this school since you've been in diapers. It's not going to wash, unless you've actually have been wearing diapers recently. And you'd be better off not telling them that!
Seriously, they will see right through this approach. By all means, let them know that you are excited and eager about entering their school, but keep it real.
This should be obvious, but don't beg and don't get all emotional saying that if you don't get into this school your life is over. It isn't over, they know it, and you'll only come off as being desperate, if not a bit imbalanced. Besides, you want them to see you as a winner - and a winner will succeed no matter how many times they are rejected. That's MBA material.
Talk smoothly, and don't be afraid to pause and have a moment of silence. Silence can be very effective to let them soak in a bit of what you've said. Of course, don't be too silent, though!
You do want to speak with confidence but not be too cocky. This can be a hard one for younger people to pull off. They usually go to one extreme or the other. Either they're too humble or they come off as a total jerk. Find a balance.
If you can, do a mock interview with an older person. They can really point out things you might not notice yourself, even with video.
How you handle yourself during the interview in this area is going to make a big difference. So practice your interview skills... and be prepared.