In terms of what separates candidates, given equal GMAT scores, it's going to come down to your SOP, and interview. Volunteer or humanitarian activity of some kind is important, as is (of course) your own work experience, but above all else, the schools want to see how you are PRESENTING and basically branding yourself to them, which translates directly into "how do you really see yourself as a professional?"
This then translates to "how do you carry yourself, come across to others, represent your own personal vision."
THIS is then what will truly get an admission officer's attention, which is going to equate to an acceptance over "the other guy/woman" all scores being equal.