Ooh, Kazbah, I really don't know. Natty has bitten a few times and I guess I am fortunate that it doesn't happen often because I haven't the first idea of how to deal with it.
I am a fan of sitting them down and making eye contact... but you are right, it is difficult when they don't understand the relationship between the action and the consequence or punishment.
I know that I am way over the top whenever Natty hurts me (e.g. pinches hard or hits me with something) and I haven't seen it coming or haven't been able to prevent it. I yell "OUCH", like, really loudly. (And a lot of the time it's because it really hurts!) Then I will sit her down and look in her eyes and tell her firmly that she mustn't hit/pinch because that hurts people. If she gets upset then I give her a cuddle straight away. I generally don't leave her alone - I feel like she's a bit young (and she's a pretty emotional kid) just yet.
Good luck, mate.