I try to keep cool in my home for as many months as I can before giving in and running the expensive air conditioning unit or swamp cooler.
Ten Easy Ways to keep your home cool before putting on the AC:
1. Keep windows open so you can get a cross-breeze.
2. Put a table or box fan in your window.
3. Leave the window open at night to draw in the cool air while you sleep. A fan in this window is a nice addition.
4. Keep the blinds closed on windows that receive direct sunlight, and all south facing windows. Add thick curtains that block light and heat, or tack up blankets/tapestries over these windows during the hot parts of the day. White or shiny linings that face outside will help the heat bounce right away, too.
5. You can use a plant mister to spritz the air and keep things cooler, if you live in an area of dry heat. Having house plants around helps, too.
6. Keep doors (especially on the south facing side of your house) closed during the hot part of the day. You can open the doors in the afternoon or evening to let in cool breezes.
7. Think about tacking up thick curtains over south facing doors during the day to help keep the heat out.
8. Set up shade outside your home to prevent direct sun from shining on your roof and walls. You can plant shade trees or thick vining plants, set up bamboo sun screens, or simply hang wet sheets from a line to promote evapotranspiration.
9. Do not cook inside! Set up cooking stations on your porch or balcony. Make coffee, use a crockpot or hotplate, or any other appliance with heated elements, all right outside the kitchen door. You can BBQ in the yard, too. Run your laundry cold. Place hot food outside to cool off after cooking. Line dry your clothes instead of using the hot clothes dryer. Keep those hot incandescent light bulbs off, or trade up to compact florescent and LED bulbs. Don't create ANY waste heat inside your home!
10. Take cool showers and baths during the day. No need to run your typical hot shower each morning when you can wait for the hot part of the day and cool off a little. This is good on several levels. You won't create steamy heat in the bathroom that wastes the cool air gathered overnight, and you can enjoy the nice sensations of water evaporating from your hair/skin for an hour or so. Don't be in a huge hurry to dry off, either.
Okay, here's an eleventh tip, absolutely free: Think like a desert creature. A lot of staying cool lies in not letting your core get hot in the first place. Treat your body like a cold glass of water - ie, don't set it in the sun! Don't sit, stand or work in the direct sun, avoid the hottest hours of the day by staying indoors from 10-3pm, and try not to exert yourself physically. A desert creature is active in the early morning, in the cooler evenings, and late at night. They siesta during the day! Work your schedule so you do sitting activities in midday, and get your active time/chores done in the cooler hours.
Basically, this all boils down to: remember to conserve the cooler temps your house gets for free, and prevent the accumulation of added heat to your body and home in the first place.