One is the curriculum the school offers. If possible, visit the perspective school. Contact them and ask about the school's record. Contact the Better Business Bureau that covers the area the school is located in. This is a good indication of the satisfaction of prior students.
Schools come and go every year.
These are probably the easiest and most important first steps to making a decision that will most likely affect the rest of your life. You can not ask too many questions and any school genuinely concerned with the welfare of it's students should be willing to answer these and any other relevant inquiries. The choice is yours.