My answer, originally published on Quora.
Q: What do MIT admissions interviewers look for?
I used to interview applicants to MIT, and the biggest things I looked for were:
Deep intellectual curiosity and a passion for learning that goes far beyond the norm. This was best demonstrated by extreme dedication to one activity, cause, or line of intelectual inquiry -- well beyond taking and excelling in the classes and activities offered at your school.
Do all that, but then take it to another level, and then another level beyond. Become a self taught expert. Seek out the advice and mentorship of true experts. Get involved at the state level or the national level. Share your knowledge and teach others. Go beyond.
The choice of activity itself is not as important as the dedication, passion, and resourcefulness you bring to it.
Self motivation, tenacity and grit. Candidates who had to overcome extreme circumstances (poverty, health issues, etc.) have an easier time demonstrating this type of perseverance, but even a privileged candidate with a thus-far easy life can demonstrate it by taking on challenges that push his/her skills and stamina beyond their limits.
If I got the impression that your parents were more responsible for your achievements than you (because they paid for your trip around the world or for you to attend a fancy summer school) then I would not give you a good recommendation.
Lack of arrogance. I've met applicants who acted like MIT would be lucky to have them, that admission was some kind of entitlement. Others showed disrespect for me and my time by showing up late or dressed like slobs who didn't care.
A burning desire to attend MIT above all other schools, and can explain why.
Virtually all the candidates I saw were outstanding students who were very involved in extracurricular activities. As an interviewer, I did not ask about grades or test scores because the admissions committee already had access to that information.