Firstly, I dont post anything on here, i just read, because I am far from an expert. The responses on this topic though are scattered and varied and will do nothing to help answer your question. I, will add my amateur "opinion".
Panning is not easy and takes practice. The results of your panning attempt will depend on what you like. No one ever said that the object you are panning has to be completely "in focus". If though, that is your intent, it is best your moving subject be at roughly the same distance from you during your panning sequence. A1 servo is the desireable setting for continual focus tracking. All apeture has to do with panning is the amount of light you require for correct exposure.
You shutter speed has everything to do with it, but mind you, the shutter setting will be proportional to the disatnce from your moving subject. I dont want to get into it, but the samples DRoberts has shown (in my opinion) do not show examples of panning, not that they arent' good photo's, just not good examples of panning for me. Unfortunately, I cannot post any images myself for a comparison, as soon as I can, I will. Anything around 1/1000th is way too fast (unless your panning a bullet). The whole idea of panning is to have a distorted lineal background and sharp subject (at least part of).
To wrap all this up, practice the following:
I use manual most of the time.
* Set to A1 Servo
* Set your drive to continuous
* Adjust your apeture for correct exposure
* Your subjects path should remain at the same distance from you for best results (get the basics down first!)
* Depending on the distance of your subject and the speed it is travelling, set your shutter to anything from 1/15 to 1/125 (try different SS for different results).
* Pick your subject (say a car) and half press the shutter release for AF.
* Pan with it and shoot a 4 or 5 sequence burst. Even after the final frame, pan with the subject to have consistency in your blur.
Hope I havent confused you more. You dont need to wait to go to a drag strip for practice either. There is a million subjects to practice on right at your feet.