Generally the price as well as the way they cut my hair. Not all people at hair salons listen when I ask for something so if I get bad service I won't go back there.
My dads gf cuts my hair :p but before we'd go to what ever place had a reasonable price.
The stylist, I look at their hair and personal style then ask myself if I like it.
The location and friendliness of the emplouyees
Quality & price.