When selecting a hair salon, you should take a number of factors into account, not the least of which is their prices. Also important are location, hours of operation, general ambience, the experience-level of their stylists, and the range of services the offer.
If you're ever stuck with a last minute need to get your hair done, keep in mind that not all salons welcome walk-in customers. Big-name, popular salons may be booked up for weeks. Your best bet for a walk-in job is one of the chain salons like Hair Pro or Fantastic Sam's.