Peer mentorship is not as helpful at this stage in life. You have opportunities for alum and professional mentorships, some professors are incredibly helpful. You can volunteer to mentor undergrads if thats your thing. Clubs will provide lots of support in prepping you for your careers and many will match you with 2nd years to help you prep for interviews, advise you on recruiting and the like. How you utilize that relationship is up to you and the other person.
My advice is you are better off getting a mentor who is an alum or a professor than a fellow student.
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Kellogg Class of 2010...still active and willing to help. However, I do not do profile reviews, don't offer predictions on chances and am far to busy to review essays, so save the energy of writing me a PM seeking help for these. If I don't respond to a PM that is not one of the previously mentioned trash can destined messages, please don't take it personally I get so many messages I have a hard to responding to most. The more interesting, compelling, or humorous you message the more likely I am to respond.