DS is 2.4. So far I have been demonstrating please and thankyou, using them a lot myself and telling him / showing him where he should use them. He probably says thankyou a bit less than 50% of the time and please about 25%, with usage of both increasing.
We still get a fair amount of "get more xx NOW" though.
I'm currently on maternity leave, we have a nanny 2 days a week (I am lucky I know), and a few times i have been caught in the middle of her not giving DS something unless he says please (his response is to come and ask me, I back her up btw). I've never really fancied this approach, especially not now when he is getting used to his new sister.
So how do / did you do it?