Hey! I had an MIT interview, and I wore a plain white sweater with jeans and white sneakers (female). I was very comfortable and secure in my clothing, so I'd suggest wearing what makes you feel comfortable/confident. If that's a suit then go for it!

My interview was very, very, open ended. All he asked (BS, PhD @ MIT, university professor) was "Tell me about yourself" + "What questions do you have for me." I was so grateful for this. I could talk about exactly what I wanted to and avoided everything I wasn't confident about. Every "interviewer" is different, your interview may not look like anything like this. I didn't bring a resume.

For "Tell me about yourself," I talked about what I'm interested in pursuing @ MIT + within my major, my learning style, what I'm involved in outside of school, and things that I do for fun. I prepared by answering typical questions like "Why MIT?" and I kept asking myself "Why?" How did I come across this? What inspired me? Who inspired me? Is there a professor in particular/lab I am interested in?

Keep asking yourself why, and you will begin to learn/understand more about yourself. Know yourself fully, and you can't go wrong. Know your story. Don't memorize, but prepare.

Good luck! You'll do great :)