1. Close your windows
It may seem counter-intuitive, but opening the windows will often make your home warmer, not cooler. Open your windows at night if the air outside is cooler than inside, and close them -- along with blinds and shades -- before the sun hits your house in the morning. This will allow cool night air to circulate, and prevent a good deal of the sun's heat from infiltrating your living space.
You may also put houseplants -- particularly larger potted trees -- in front of sunny windows to absorb some of the sun's energy. Use this method, and on all but the summer's hottest days, you can get away without using the air conditioning at all!
2. Use fans strategically
Ceiling fans and those set right in front of you are there to keep you cool, not cool the room. But a fan in your face can help you feel dramatically cooler, even if the room temperature hardly budges. You should be able to set your air conditioner higher, at about 78 degrees, but feel much cooler by using a fan.
Enhance its effect by wetting your skin with a spray bottle, and get a near-instant cooling effect by wetting your wrists and letting the fan blow air across them.
Fans can help cool your home, particularly when used to blow cooler air indoors, usually at night. You can maximize the effect by creating a wind tunnel of sorts, with a fan blowing cool air in on one end of the house, and another blowing out on the opposite side of the house.
3. Adjust the thermostat
If you have central air controlled by a thermostat, program it to save energy by increasing the heat significantly during the day when the house is empty, and give up a couple degrees at night, too -- especially on the hottest days.
You may be surprised to find that the contrast between outdoor and indoor temperatures matters as much as the absolute temperature inside your home.
4. Cook a cool meal
Just as drinking a nice cold cocktail cools your body, eating cold food helps keep your internal temperature lower on a hot day. One great option: Watermelon and Cherry Salad with Fresh Mint Syrup.
If you do cook, use the grill or the microwave, or else you'll heat up your kitchen from using the oven and stove.
5. Shut off the lights
While modern lightning, like compact fluorescents and LEDs, are more efficient, incandescent light bulbs can produce as much heat as they do light. Energy Star-rated light bulbs produce 75% less heat, so consider that when replacing bulbs.
It's always a good idea to shut off lights to save energy, it makes a big difference on hot sunny summer days. The same goes for many electronics, so consider unplugging any device that isn't needed (even in standby mode, many electronics remain hot).
6. Clean the air filter
Whether you have central air or a room air conditioner, a dirty filter will reduce its efficiency, making it use more energy and cost more money to do the same job. Check your HVAC system's air filter monthly and expect to change the filter every three months.
7. Go for a swim or take a cold shower
It may sound obvious, but it's worth saying: Cooling your body is as effective as cooling your room. One easy way to cool off is to immerse yourself in cold water. The immediate refreshment works immediately by cooling your core temperature. And unless there's 100% humidity, the evaporation of water off your skin will further cool you.
For a short cut, use water and ice cubes to keep your wrists cool; since your blood vessels are so close the skin there, you'll feel cooler by applying cold directly to your blood. Check out these stunning natural swimming pools.
8. Get an annual checkup
If you have central air, consider an annual checkup -- once should cover both the heating and the cooling season. A professional should be able to diagnose any inefficiencies before you've wasted money on monthly heating and cooling bills.
9. Plant a tree (or two or three) strategically
Your house gets hot because the sun beats down on it relentless on hot summer days. Let nature help reduce your energy bills by planting deciduous trees on the east and west sides of your home; in the summer, their broad leaves will shade your house, while in the winter, bare branches won't stop the sun's warmth from reaching your walls.
Also consider planting trees or shrubs to shade high-heat areas -- air conditioning units that emit heat, for instance, and driveways and walkways that absorb it.
10. Install attic insulation
While attic fans may or may not help significantly to cool your home, attic insulation can help a lot. Insulation keeps cooler air in your home from escaping through the ceiling.
If you have central air, also seal ducts -- especially at vents and registers, where you could be losing up to 20% of you cooled air. Do the work this year to take advantage of a tax credit covering up to 30% of the cost of insulation, up to $1,500.
11. Put up awnings
Just as window shades and shrubbery work to shield your home from the sun's rays, awnings can cut down on the heat your house absorbs. This is an investment to make if you like the look.
12. Think small
Cooling one room with a window air conditioning unit requires much less energy (and investment) than a central air system. If you're in the market for a new air conditioner, ask yourself how you'll use it, and choose the smallest option that works.
13. Buy Energy Star
Whether you're buying a central air conditioner (which could qualify for a tax credit worth 30% of the cost, up to $1,500) or a room unit, efficiency matters. An Energy Star central air system will use just 86% of the energy it takes to run a typical air conditioner that meats minimum government standards, and a room air conditioner will use 90% or less.