Simply put - Go and see them! Search for the training thread on this forum and glean as much info from it as you can before you do so though.
Choosing a school is about weighing up cost, type and availabilty of training machines, personalities of instructors, distance to travel, facilities on site.
Be slightly cynical and trust your gut having seen all the schools available to you.
Let them know they are being checked out and see how they react...