I never forced the chatterbox that is Liebling to say "ta" or "thank you". He does it naturally because I do it to him. Once he could say "thank you" then I sometimes prompted it, but it was always a song and dance when he did rather than punishment when he didn't. He doesn't get things if he doesn't say "Please" now - but he tends to treat "please" as "you said no but I still want it so I'll try something else" rather than as a nicety.

Now he's 3 just a look from me will get a "please" or a "thank you" because he knows it is expected - but if I don't have to verbally prompt then he gets a kiss with whatever he's asked for. Cos I like kissing him!