Typically a standard set of socket wrenches or box end wrenches are all that is required to change a drive belt on an automobile. In some cases, a ratchet extension may be required depending on the location of the tensioning bolt. Some older vehicles may require a tensioning bar as well.
Older model vehicles may have multiple belts driving devices on the engine. Newer vehicles typically incorporate one serpentine belt to drive all of the equipment needed to run the vehicle.
Vehicles using a serpentine belt have a spring-loaded pulley that works to tension the belt. Put the correct-size socket on the center nut of the pulley, and pull the ratchet handle forward to release the tension. If the tensioning bolt is recessed too far behind other engine parts to reach with just the socket, attach an extension. Remove the belt, replace it with the new belt, and release the tension.
Locate the tensioner pulley on older vehicles by identifying the pulley attached to a sliding mount that has a slot allowing for forward and backward movement. Loosen the hex nut with a box wrench, and slide the pulley forward to release the tension. Remove and replace the belt. Use a tensioning bar to pry the pulley backward to the correct tension, and tighten the bolt.