Hello! I was waitlisted from Harvard and I’ll be in Cambridge this week (for the MIT preview weekend). Harvard is my dream school as it combines both the program and environment that I’m looking for. Would it be worth it to visit Harvard admissions to possibly re-interview or talk to admissions? I figured this may be the best way I could show my interest in Harvard. However, I don’t have any major updates to my files so do you have any recommendations of what I should say to the admissions staff? Thank you, I appreciate your time!
Truthfully, that’s going to take your focus away from MIT – and you shouldn’t do that. You need to fall in love with the school that loved you back, and not act like a lovelorned schnook who’s been jilted (sorry).
FWIW: Harvard Admissions doesn’t care about a student’s interest, and your show of interest in the school will not help you get off the waitlist. While you are at MIT, do yourself a favor and investigate the ability of MIT students to cross register for Harvard classes. Now, that might be worth your while!
Agree with @gibby. You need to go and fall in love with MIT and learn to hate Harvard like the rest of MIT!
Back in my day during the cold war, the motto was “Better dead than Crimson!”. 
What should I not do?
Here are some things you should not do: Fly to campus to make the case in person. Send us ridiculous items or bribes. Submit a whole new application. Bombard our office with way too much stuff. Be pushy. Be sketchy. Let your grades drop. Not choose another college to attend by May 1.
What should I do about the May 1 reply date for other colleges?
You should accept the offer of admission from another college before May 1, even if it means making a deposit. After May 1, when all students have sent their replies, colleges will determine if they need to go to their waitlist or not, and if so, how many students they need to admit. At this point, colleges will begin admitting students from the wait list. Students who accept this offer will “unenroll” at the first college and enroll at the second. This shifting can lead to a second round of wait list admissions. All of this is a standard part of the admissions process. We colleges recognize and accept this.
Harvard admissions will not meet with you. That’s their policy, so I wouldn’t waste a trip. An email or letter is fine and more than sufficient.