I am workin on sweet home alabama and the hammer ons and pull offs do take some practice, I am not sure about the official form or anything but I think, getting the timing and rythm down helps me know just how fast to hammer it on or pull it off, I think the faster you hammer on, the better it sounds but thats just me, or maybe I'm just crazy :eek:
The greatest enemy to what you can know, is what you already know.
It's not how good you play, its how well you play it.