I would say look for a school that does not take all your money up front, I was very comfortable being able to pay for any flight/ground time at the end of the session. I've heard of folks that make big payments up front and then the school goes bankrupt for whatever reason, you will likely not see that money back.

Other than that, look at any accident history and maintenance on their planes. Compare rates and try to do your training somewhere with nice weather where you can fly anytime you want.