Next Belts should be looked at fairly carefully every 10,000 miles, or so. There are typically one to three rubber belts driving various components such as the alternator, power steering pump and air conditioner compressor.
Some cars have a single serpentine belt that drives everything.
If one or more show signs of glazing, cracking, or wear, replace it or them. Keep any old, but still usable belts in the trunk. You can easily check the belt tension. Belts should be tight, but not too tight, otherwise they will wear out prematurely, or cause wear on a driven component. Press firmly with a thumb or index finger at the center of one of the wider spans of a belt between a couple of pulleys.