You should always keep doors and windows closed to the outside.
Do not cool any rooms that are unoccupied or close more than half of the registers if you have any in the home. This can cause your unit to malfunction if there is too much restriction on the air flow.
Set the thermostat higher on any ceiling fans. If there is humidity, keep fans on a low speed.
While your home is unoccupied, set your thermostat to 78 F or higher. Setting the thermostat lower uses more energy and only cools a warm room colder, not faster.
Consider a programmable thermostat for central units. Some can be easily controlled from your smart phone or computer. These are especially good if you are away from your home at the same times during the week.
Keep your air conditioner from running longer than necessary by keeping electronics away from the thermostat, such as televisions or lamps, as the thermostat can sense the heat.
To extend the life of your air conditioner, maximize your comfort and save on monthly energy bills, consider calling a professional air conditioning maintenance contractor to tune up your system before the season.