Research Interest
Cost of Living
Weather/Location
Distance from Home
Everything Else
Distance from home is the only above factor that didn't disqualify any schools. I would like to take all my stuff with me without any hassle (TV, computer, clothes, books), so I would very much like to go somewhere <1000mi. I would also like to live close to my family, but I live in the Los Angeles area so this directly conflicts with cost of living and weather. Anywhere outside Southern California is flying distance to me so might as well all be the same.
There's enough schools out there with good whether (I prefer cold to hot) that I mainly applied to those. Washington, Oregon, and Colorado were my top picks for weather. Arizona was not eligible for my list (I have no desire to live in Phoenix).
Stipends seem to factor in the cost of living, so this isn't a huge issue. There were some significant differences, though. At MIT I might be sharing a minuscule two bedroom while in New Mexico I could get my own fairly large two bedroom with a balcony and swimming pool for a similar price (adjusted for stipend size). I would like to live comfortably during grad school and I'm willing to make sacrifices in other areas for this. I intend to bring my girlfriend along, so I would like to have a second bedroom separate from the living area that I can turn into a study.
Weather, cost of living, etc. are all important factors, but the deciding factor is always going to be research interests. I'll live somewhere less than optimal and will abstain from somewhere wonderful for the sake of research interests.
That being said, all of the above are important enough factors that they could end up overpowering any of the others. Most of my schools were pretty even in all areas, so it's going to be a tough call for me. Optimally, I would like a few professors with similar research interests in a mountain town, 20-80°F, <1000mi from L.A. with affordable two-bedroom apartments and politically similar people/government. If I could take U. Michigan or U. New Mexico and stick it in Boulder, that would be perfect.