I am an MS-IV. From what I understand, most admissions committees look for applicants who have a track record of academic stability (i.e., flat or upward trend in grades and no C- grade or lower) and those who have strong MCAT scores to correlate with the GPA. They look for these things because what they really want in an applicant is an applicant who has the ability to complete medical school.
Because MCAT correlates well with first year performance, they tend to look at that first. Then they look at the GPA and major. The specific coursework isn't very important. What's important is the GPA. Then the committee would note if the applicant went to a competitive and reputable undergrad program. A college with a great reputation adds a nice veneer to the whole application. Seriously.
What they read next is the personal statement. They look to see if you're literate and if you have any serious personality problems (e.g., conceitedness, insincerity, dishonesty, cynicism, slothfulness and other qualities that would cause problems for the hospital staff and patients) Then they assess to see how motivated and goal-oriented you are.
What they look at next is the extracurriculars. Again, they don't have much time to read (they have thousands to go through!), so listing a myriad of activities doesn't excite them as much as they had for college admissions. What they look for here is leadership potential and the ability to work well with others.
The part of the application that is overhyped is the letters of recommendation. Unless the letters are from MDs or clinical investigators with huge NIH grants, they don't bear much weight. Nobody really knows what it takes to be a doctor unless he or she has at least gone through medical school. So a letter from a PhD saying how you'd make a good MD seems rather silly. A supportive letter of recommendation that states how you're a basic science god is more helpful than one that says how you're a compassionate, thoughtful human being (although that wouldn't hurt).
If you are offered an interview, congratulations! All the hard work you had put in your apps paid off. At this point, the interview is the most important factor for admissions. You already made the first cut, which is to see if you can hack the medical school workload. The interview is there to see if you are the real deal and to make sure that you have the social skills a doctor must have; the interview is also a good time for the committee to sell the school. A qualified candidate who accepts an offer of admission is one less applicant to screen and interview, which means less work for the commitee!