Set your air conditioning thermostat to 78. Go higher, if the humidity is low enough and you feel comfortable.
Drink lots of water. Cold drinks drop your body's core temperature and cool you down quickly.
Keeping your blinds, shades and curtains closed. It helps keeps heat from getting inside your house.
Do laundry early in the day and late at night. Don't forget clotheslines: they generate no heat in the house.
Skip your dishwasher's dry cycle. Let them air dry instead.
Open the bathroom window when showering. Vent heat and humidity outside, rather than back into the house.
Limit cooking in the oven on hot days. This tends to really heat up the home quickly. In fact, grill out often to help keep the home cooler and save on energy.
Switch off your computer and lights when not in use. They generate heat.
Plant trees on the south and west sides of your home. They will provide enough shade in the summer (and wind blockage in the winter) to save you between $100 and $250 in energy costs annually, according to the US Department of Energy estimate.