Some people would disagree, but panning is quite a difficult technique to master and do it well. I would say that 75% of a successful panned shot is down to a smooth panning action by the photographer.
What else is important is the shutter speed, this is where bad advice to someone new to this can cause everything to go wrong. Don't start with shutter speeds of 1/100 or 1/125 sec, start with a higher shutter speed of say 1/400 sec practice the technique, then slowly bring the shutter speeds down, of course this will depend on how fast the subject is going and what lens you are using.
Remember to pick up the subject early enough and track the subject, panning with the action until you are ready to take the shot, take a small image burst of 1 to 3 images, remembering to continue the pan after the shot.
Its all about practice, correct positioning and not jumping ahead of yourself before you are ready and comfortable to do so.
Peter
Also remember that the autofocus point doesn't need to be camera centre, think about how the car, bike is moving and adjust the autofocus point to match, in this case I was focusing right of centre.
