Decide what kind of fan and how many fans are needed. Consider factors such as the size of the room and its number of windows. Select fans that have the appropriate size and power to cool the room.
Select the appropriate place for the fans. Fans should blow in from the cooler side of the house. Consider other factors such as the normal temperatures and humidity where you live. If the temperature outside is cooler than the room but the humidity is high, the incoming air won't cool the room. Place fans only in windows with screens to keep insects out.
Place a fan in the window and have it blow air in when the temperature outside is cooler than inside the room. Use as big a fan as possible that will fit the window. Make sure the fan securely fits in the window.
For a room with multiple windows, place fans in windows at opposite sides of the room. Have one fan blow air out, and one fan blow air in. This will circulate the air and cool the room. Place the fan blowing out as high in the window as possible. Place the fan blowing in as low as possible. Hot air rises, so this will help blow hot air out of the room, and blow cool air into the room. You can also place the fan blowing air into the room low to the ground in a doorway.
Place an ice-cold towel across the side of the fan that is blowing air into the room. Make sure the towel fits the size of the fan. The air will cool as it passes through the towel.
Take fans out of the windows when not in operation. Close blinds or curtains to keep sunlight out of the room.