Originally Posted by Napasanaoma
A word about resurfacing; You can not only visually inspect a rotor you need to check the surface with a dial indicator. It does not does not take much difference in two parallel surface to not have even pressure and contact. Brakes wear in and can cause a rotor to wear slightly uneven and to get the best performance out of a new set of breaks you should resurface, or at the very least check it with a dial indicator. The breaks are one of the most important devices on your car. Visually you can check for grooves and burns, but uneven surfaces you need instruments.
Good advice. Personally, I resurface every time I put on new pads. That way they get a chance to get introduced on an even surface, so to speak. Putting new pads on a worn rotor will actually reduce your stopping power until the pads get a chance to get "bedded in" to the groves on the rotors.