If possible install the unit on the shady side of the house . Invest in a setback thermostat . Why cool it down when you're not home. The coils of the unit can become plugged, also make sure there is a minimum of 18 inches between the unit and any plants or shrubs. Change your furnace filter .
Many people forget the filter is used for heating and cooling.
Pull the plug . Make sure the drain for your furnace is free of debris. Your air conditioner cools by removing the humidity from the air inside your home. This is turned back into water that needs to be drained to assure your air conditioner's top performance. During the summer, leafy, deciduous trees seem almost made for energy savings.