Locate your air conditioner filter. It will be located along the length of the return duct, in the wall, ceiling, furnace or the actual air conditioner. Clean or replace the filter every 2 to 6 months. Change it more often if you have furry pets, live in dusty conditions or use the air conditioner often.
Check the outside condenser coil every year. Rake away leaves and other debris, and use your pruning shears to trim branches back at least 2 feet away from the coil. If you notice actual dirt on or around the coil, wash it away with a garden hose.
Check the evaporator coil once a year and clean it when necessary. If you change the filter regularly, there shouldn't be much dirt on the evaporator coil, but it can build up over time in older units.
Remove the screws on the front grille if you notice a musty odor. Remove the grille to expose the air conditioner drain hole. Examine the hole to make sure water can drain freely. If the drain is blocked, unblock it with a wire clothes hanger and replace the grille.