-What should I wear?
It's better to over dress than under dress for an interview, but try to keep business casual in mind. Wear what you would to a nice dinner or to a night out to see a play. Since your interview is in summer, I think a nice polo shirt with good pants would be appropriate, especially since you aren't going to want to be weighed down with something like a pantsuit.
-What should I bring? (there are things I could consider like the lit mag of which I'm EIC, pictures with a legislator, different awards... tidbits like that)
Out of what you listed, I would bring the lit mag alone. Everything else can just be spoken about in the interview, but a magazine has to be experienced.
-What should I expect? What do they want from me?! Is there a common denominator "interview question" that I will most definitely be asked?
I didn't interview for Wellesley, but I did for Smith. If the two are at all similar, you can expect a low key discussion more than an interview (but I'll leave this to really be answered by someone who did their interview at Swells.) For any interview, though, as cliche as it sounds, just relax and be yourself. If you're even looking into Wellesley, you're undoubtedly an accomplished woman with many different interests. Bring some of them up. Don't try to put up a front or say what you think they want to hear.
-Will they say "tell me about yourself?" -- I think this question is a crime against humanity...
They shouldn't...but they might. Certainly every question that WILL be asked will be a more specific variant of that, though, so it might be a good starting place for you to prepare. I would sit down and ask yourself that dreaded question right now, and when you answer think about...
- the classes you've enjoyed and why it was that you enjoyed them
- the people who have influenced the woman you've become
- the activities you do outside of school and the reasons why chose them
- the quirks that might not define you, but certainly are a part of you. Maybe you always read magazines back to front (I do *embarrassed*) or you hate the question "tell me about yourself" ;p
I think when you start to answer these, you'll come up with common threads , and you'll paint a very clear picture of just who it is that you are. And hey, even if you don't, you just answered questions that really are bound to come up...well, except for the quirks thing. I just happen to find that an interesting part of everyone haha.