How many schools?
The simple answer is, somewhere between 6 and 20. Not such a simple answer, I suppose. It really all depends on how much of a chance you think you have of getting in anywhere. If you think you are absolutely stellar, above and beyond pretty much everyone else you can imagine - then 6 schools should work out. If you've got some GREs and GPAs that you wouldn't exactly write home about, or very little experience, move up toward the 20 range.
Now, really, is anyone going to actually apply to 20 schools? Of course not. But I suggest choosing 20 schools, and shooting for that number, because at higher numbers, you probably will drop at least four of them when it actually gets down to crunch time. And that's OK. Applications are ridiculously stressful, and you can almost count on yourself getting a little overwhelmed and deciding not to apply to several of your lower-choice schools in the end. So, to be safe, I would suggest choosing about 4 more schools than you feel safe applying to.
