Emma, I normally do positive modelling and gentle explainations.

DS isn't perfect but he's not too bad. His main failing is running onto the road. Which means we usually use reins or I block him (or play crossing roads with him for hours if it's safe to do so) - if he is getting REALLY insistant and it's dangerous then it's the pushchair. But he's polite and kind and loving, if he does something we don't like then we first distract him, then if he continues we explain we don't do that because... and that seems to work wonders.

But how to let him know it's OK in one situation but not another? I've not really had to do that before, because pushing or biting is never OK so he doesn't do that (much!) to anyone - in fact, I'm the usual victim of that (because DS is tired or hungry so he comes to me then).

I'd love him to do this to me, but I do know that other children don't like him being so loving, especially if they don't know him too well.