Blurred Background, Sharp Subject...
Panning is a technique that I am sure many of you already know or use. For any moving subject it is important to "stay with" the subject whilst you are framing the shot before, during and after you shoot.
Using slower shutter speeds, this technique can ensure that the subject stays sharp even if the background is blurred, an effect that is quite striking particularly in sport.
A simple way to try this is to stand by the side of a road and pick out a car coming towards you;
Set your cameras shutter speed (TV for Canon, S for Nikon) to either 30th/sec or 60th/sec, this will be slow enough to cause movement as you swing or pan the camera. The aperture and depth of field are somewhat irrelevant as the background will be blurred anyway.
Make sure that you aren't too close to the road. Basically for your own safety and secondly if you are too close, the car will become distorted, especially with wide angle lenses. A small telephoto like 85 or 100mm is perfect for this technique.
Either pre-select and manually focus on the point directly in front of you where you want to take the shot, (this will "fix" the focus on that point), or set the autofocus to AI servo( for Canon users), (AF-C for Nikon) in order to "track" the moving car.
Aim your camera at the car and stay with it with your finger lightly pressing the shutter button halfway to either track the focus (in AI servo mode) or/and to get a constant exposure reading.
At the point where it passes your pre-designated shooting area, fire away, whilst "panning" with the car all the time, and even use continuous mode if you have it to ensure one shot comes out well.
Obviously you can try this technique with any moving subject but you will have to factor in the speed of the subject when choosing your shutter speed. For example, you can pan when shooting someone walking or running to create the effect of movement on their arms and legs whilst keeping their body sharp, experiment with different speeds until you feel confident and happy with your results