Get an Energy Audit
Many utility companies offer a free home energy audit to customers, and it's well worth taking advantage of. If there's no such program in your area, conduct your own energy audit instead. It'll clue you into areas where you could trim your energy use.
Install Dimmer Switches
Then, only use as much light as you need.
Keep Your Fridge and Freezer Full
Food acts as insulation, and lessens the amount of time that the fridge has to run to stay cool.
Install Ceiling FansKeep the air circulating in your home, and your air conditioner won't have to work as hard.
Line Dry Your Laundry
Set up a clothesline in your back yard, and let Mother Nature dry your laundry. If this isn't an option, consider hanging clothes on a drying rack or on the shower rod.
Eliminate Phantom Loads
A surprising 75% of the energy used by home electronics is consumed when they're turned off. These "phantom" users include: televisions, VCRs, stereos, computers and many kitchen appliances--basically anything that holds a time or other settings. A simple solution? Plug all of these items into power strips, and then get in the habit of turning off the strips between uses.
Install an Attic FanIt'll pull cool air into your home, and help to remove the hot air.
Shield Your Home From the Sun
Cut down on your air conditioning use by closing curtains and blinds on the sunny side of your home. For even more savings, consider installing tinted window film.
Schedule Yearly HVAC Maintenance
Increase the efficiency of your HVAC system by having it inspected and cleaned once a year. Added bonus: cleaner air in your home.