Freeze the action
When you're shooting fast action, shutter speed is the most important camera control you have, so use the camera's action or sports mode, or set the camera to shutter priority and dial up the shutter speed as high as possible.
What's a fast shutter speed? If you're at a car race, an air show, or a sporting event with lots of fast action, I recommend 1/1000 second or faster. In fact, no shutter speed is too fast if it lets you get a shot that you wouldn't be able to get otherwise.