Preset the focus
Often, the biggest time waster when you're trying to snap a photo is waiting for the camera to lock the focus — especially if the camera has trouble finding the subject and has to hunt for the appropriate focus.
You might already know that if you press the shutter release halfway down, the camera locks the focus. As long as you hold the button down lightly, the focus will stay locked while you compose the photo or wait for the perfect moment to take the shot. If your subject is darting around in front of you, lock the focus and keep tracking the action. At the right moment, finish pressing the shutter, and you'll get a much more immediate reaction from your camera.
Another option is to skip the autofocus entirely and set the focus manually. I recommend this approach if you know that the subject will always be very far away, such as airplanes at an air show. In that case, switch the focus to infinity. Just remember to set it back to autofocus when you take pictures of things that aren't quite so distant.