When I faced one of those tough, vague, secondary questions, I wrote a reply in short story format...about a moving experience I'd had as a volunteer with one particular patient. I guess the advice I'd give is to do something different than what you think the other applicants will do, because you have to realize that the admissions committees have to read a zillion of them each year.
They're not easy to do, I know...but the vagueness of the question can be used to your advantage, if you think about it: this gives you freedom to take any angle you choose. There is no "right" way to do it...just pick something and go with it.
Some people try to convey to the admissions committee why they are a great fit for the school.
I think this is something you can do better if/when you interview at the school. A letter of intent (sent after the interview) is a good forum to tell the admissions committee why you'd be a good fit for that particular school (and it's from a better informed viewpoint, since you've now actually seen / experienced the school in person rather than just on paper).
Bottom line: try to convey your enthusiasm / passion for being a good doctor, without sounding too braggy about yourself. Also, spend a lot of time on these (they're more important than your school exams, as far as I'm concerned)...what you may not realize is that while you're writing these secondary essays to get accepted, you're also writing them to get SCHOLARSHIPS if/when you are accepted...(I won two scholarships this way). Pour your heart and soul into them.
Best of luck.
