Proper attic ventilation is important year around. In hot weather, adequate ventilation keeps hot air from accumulating in the attic and causing more heat in the house below. Turn off lights that you don't need. It saves energy and cuts down on added heat during the summer. Use compact fluorescent lights instead of regular incandescent light bulbs.
Fluorescent lights are cooler and use less energy.
Use ceiling fans or small fans to help circulate the air in the summer. Moving air makes you feel cooler, so you can set the thermostat at a higher temperature and still feel comfortable. Turn down the thermostat on your water heater. 120 degrees is adequate for most home needs. Wash clothes in cold or warm water and always rinse in cold water.