I think most people think a ceiling fan has two settings, on and off. Of course, your ceiling fan also has multiple speeds, but you still may not be using your ceiling fan the correct way.
The answer is fairly simple: your ceiling fan should be switched to counter-clockwise when the temperatures go up.
Counter-clockwise ceiling fans push air down, making a nice cool breeze to assist your air conditioner during those hot days. You frequently hear the term "wind-chill" during the winter, but it's also applicable to what your counter-clockwise fan motion is doing to you in the winter.
It's very weird when you think about it. You would think that a ceiling fan moving forward would cool, but it's moving backward, or counter-clockwise, that does that trick. Pretty much every modern ceiling fan has its blades pitched the exact same way so you can be assured you're doing the right thing.
Here's some bad news you don't want to hear. It's advisable for you to clean your ceiling fan before changing the directions. If it's been a minute since you've cleaned it, changing directions will cause all that household dust and funk that have accumulated on it to rain down on the area below.
Daylight saving time, when we spring forward, is a good reminder to change directions, and likewise, when we fall back it's a great time to change back to clockwise. Of course, if you're a smarty, just changing the direction when it gets hot or cold is certainly the best way to go.
The first thing you should do when you get home is to check the direction it is currently spinning in because there's a high likelihood that you ever concerned yourself with the direction ever. I certainly didn't until I heard about this last year. If you find your fan is not going counter-clockwise, turn the unit off until it stops completely, then flip the switch on the side.
Stay cool, and use those ceiling fans -- they can make life a little easier on your cooling unit.