I'm all about non-science majors for premeds. It makes you more well-rounded/interesting. Since we're on this topic, let me give some random advice for any non-science major out there:
As a non-science major myself (Humanities - broad Liberal Arts major), I was asked at every single one of my interviews why on earth I majored in Humanities. I got the sense that I had to defend my choice of major, whereas with my other science friends, they were never questioned on their major choice. I am very passionate about my major and my responses showed my interest, but I got the feeling that was not enough. Although I took beyond the required premedical courses, I was told at one interview that I was at a disadvantage because I did not have as much background as all the other science major applicants.
Anyway, so if you want a non-science major:
1. Double major in science if you can so interviewers/adcom won't think you can't handle science.
2. Major in something that genuinely interests you and find a way to tie it into medicine/people.
3. Take as many hours beyond the required premedical courses as you can (For example, I took 12 hours more of biology than required as electives).
4. Count up your hours before you go to interviews so that you can tell the interviewer how many hours of science you've taken if they question you.
5. Do well in the science classes you take and on the science portion of the MCAT. I didn't do well in my lower-division science classes (mostly B's), but figured out my studying style the 2nd year of college and have gottena ll A's in upper-division. My argument during interviews: I've taken less science than my science-majored friends, but I can still make the high scores. Doesn't that count for anything?
6. Get a recommendation letter from a science professor in a class you did well in.
7. Be proud! But if you decide you'd rather major in science, do it. Do what makes you happy and it'll shine through.