For the question regarding y to come to a particular school, I normally stated that I admired the school's committment to education, research, and patient care. Also, I would go into location of the school if that seemed applicable, such as close to my home, in-state, urban/rural, etc. This was pretty much the same for each of my secondaries. But for each school, I tried to research the website to pick out something unique so at least it looked like I spent time researching the school and truely wanted to attend. But basically, its seems to be all about praising the school and stating that your interest match those of the school.
There is a book titled "The Insiders Guide to Medical Schools." If you can't borrow it from your library or from a friend, I suggest you buy a copy. It is written by medical students at each school and compiled into a book. It contains very unique information about each school that might help you when you are writing why you want to attend a certain school. It will also help you to decide whether or not you want to fill out a certain's school secondary or attend an interview.
I was meticulous in my re-search of school. I read the city's newspaper, websites, etc. to find out about the environment; read the school catalog and/or website to find out about the school; and if possible, talk to students there (this one is hard). Hope this might help.
Tower Records - tons of newspapers
Internet - of courses!
Barnes & Noble - some newspapers
Cornell asks this question in their secondary. Of course I talked about how it was in New York so there was a lot of opportunity there. But also they are mainly a problem based learning kind of school rather than traditional lecture, so if you like a particular type of curriculum that is certainly applicable too.
All good ideas. I'd also add that if there's a certain kind of atmosphere that you know you excel in (for instance, a case-study type approach vs. lecture, or a rural health program if you have experience in that environment) then you should point that not only is the program right for you, but you're right for it.