The biggest thing in looking for an instructor is finding someone who you can relate to, and can find out how you learn and be able to teach you that way.
Don't be afraid to talk to instructors before the first lesson to see if you like the person. Down the line if you find out you don't work well with the instructor be sure to ask for a new one.
The instructor and flight school staff works for you! The large investment you are going to make in them says make sure you get your money's worth!