Chris have a look at these Canon 60D video tutorials.
http://www.learn.usa.canon.com/galle...torials.shtml#
The one on back button focusing describes how to set it up and use.
What it does is enable you to continuously focus when the camera is set to Servo focus by pressing and holding using your thumb on whichever button you set on the back of the camera.
Depending on how you set up the camera this will remove focusing from the shutter button, so needs to be set to one of your custom setting. I use C3 so I can switch to back button without actually looking at the dial.
No doubt the video will be more specific.
Back button focusing is a real boon when shooting fast moving jets or birds inflight and is well worth getting to grips with and I'm shure will also be a major benefit when panning.
Harry