What kind of things do you think they're looking for in a statement of purpose? The stuff I've read about it is kind of contradictory: some people seem to think you should try to make yourself look well rounded, and try to humanize yourself, while some think you should focus almost entirely on your professional goals and mathematical experience (specifically, what you've done research-wise). How focused do you think the professional goals should be? I'm personally not ready to commit to a certain field, but it feels like I'm supposed to have my thesis planned or something.

The schools all seem to ask for why you want to attend their school in particular. Now, I KNOW that I'm not the only one who doesn't have really specific, academic or research based reasons for all of the schools I'm considering (some are getting considered for personal, location based reasons). How would you suggest talking about each individual school?
Long story short: What kind of things did (or will) you include in your statement of purpose?