In reply to Dominicandave:
I'm also in the anti-smacking camp! I can understand how you might occasionally be driven to it when all else fails, but I can't see it as anything other than condoning violent behaviour. Children learn from what we do, not what we say.
I am currently using a shouting technique. My (only just) 3 year old can be quite challenging at the moment. I found that if I lost my temper and shouted, I just felt bad and it seemed to make her worse as she was really unsettled by me losing it.
Now, I ask her nicely twice for whatever behaviour I expect from her (either asking her to do something, or telling her not to do something). If she ignores the request, we both know that the third time will be a shout or a 'big voice'. She does test the boundary, so I do have to go through with it but I am finding it quite effective. I think it works because it does shock her, and she doesn't like it, but I haven't actually lost control.
So, if she is not complying, I warn her that I have asked nicely twice and if she continues it will be a shout. I have to say, sometimes it is quite a relief to let rip, but without ever feeling like I have gone over the edge into complete meltdown!
This is for mostly low-level challenging behaviour. She has only bitten once or twice when really excited, and we found that a quiet and calm 'No, you must never bite. It hurts' has been good enough so far.
Good luck!