Worry about fit, feel and comfort first and foremost. Make sure the shoe addresses your running needs with regards to cushioning, stability, support, etc. If you overpronate or oversupinate make sure the shoe address this issue. Make sure the lasting (shape) of the shoe fits your foot. For high arches look for a shoe with a curved last. For flat feet look for a straight last. If your just starting out I would recommend going to a running specialty store to make sure you get the right shoe.