If your house is for sale in summer, run the air conditioner. If it's 90 degrees inside, buyers will pay more attention to the temperature than to the attractive features of the house.
Turn the air conditioner thermostat up to at least 78° or higher or use a programmable thermostat. Close doors to unused rooms. Turn air conditioners off when no one is home.
Run your air conditioner for a few minutes in the spring, before you need it. If you wait until the first hot day to discover is isn't working, you'll find yourself on a waiting list, sweltering sometimes for days before an air conditioning specialist can come to fix it.
Set your thermostat as high as comfortably possible in the summer. The less difference between the indoor and outdoor temperatures, the lower your overall cooling bill will be.
Change the filters regularly. Dirty filters restrict air flow, reducing efficiency and worse case, can cause the evaporator to ice up. Disposable fiberglass filters should replaced. Electrostatic or electronic filters need to be washed regularly.
Don't set your thermostat at a colder setting than normal when you turn on your air conditioner. It will not cool your home any faster and could result in excessive cooling and, therefore, unnecessary expense.
Clean obvious obstructions such as newspaper, leaves, etc. from around the exterior of the unit.
Set the fan speed on high except in very humid weather. When it's humid, set the fan speed on low. You'll get better cooling, and slower air movement through the cooling equipment allows it to remove more moisture from the air, resulting in greater comfort.
Be sure the thermostat is set in the cooling mode. Just setting the dial below room temperature will not activate the air conditioning if it is set in the heat mode.
Consider using an interior fan in conjunction with your window air conditioner to spread the cooled air more effectively through your home without greatly increasing your power use.