One way to save is turning the thermostat 10-15 degrees warmer (or colder) than normal while away from home. This will ensure that the AC/Heating unit does not run constantly while no one is home. Also, a programmable thermostat is a great investment. You are able to set the temperatures you desire for energy saving during the day and comfort when you are home.
Another key to making sure your unit runs properly is changing the filter. Filters need to be changed at least once a month, maybe more depending on your location.