Apply to a variety of schools no matter how competitive you think you are. Your choice should be based on location, experience, advisors, voodoo, etc. Just make sure they are not all in California, and not all "top-tier" (Denver, Cinci, Indy, Carolinas, etc.).
Apply to enough programs to get at least 8-12 interview offers. This (safely, albeit) means about 20 programs if you're very competitive, 30 programs if you're about average, and 40 programs if your application has some problams.
That being said, EM, in my humble estimation, is not as board-score-batty as some other specialties so don't leave highly desired programs off your list just because you think they won't be iterested - you never know, and it's only a few extra bucks.
It is almost more impossible to determine which programs are bottom-tier than which ones are top-tier. Hennepin, for instance, is on my personal bottom-tier just because of location but probably most of the other readers on this site would leap to disagree. Some of the newer programs might be less competitive because not everybody is willing to go with an unknown, but even this is widely debatable. MUSC, for example, is brand new this year but for all I know it could end up being super-competitive - what if everybody they interview has a pioneering spirit and is dying to live in Charleston?
Oh yeah, and read all the excellent stuff everybody else already said.