I spend time each day practicing discussing things with him and he has already come to assume if he wants anything in life he will need to talk about it as throwing a fit or whining ensures he does not get anything.
People assume because kids haven't been trained, they can't be trained. So they wait until they are older (or even at college level) to begin training. Really bad idea.
Is a good start - then I build from there. We're working on the 'understanding' part of critical thinking right now since he is still trying to make sense of the world.
A) Whining isn't a nice way to ask. [start conversation about manners...]
B) No. We just ate lunch. [start conversation about eating when we all eat..]
C) No. Do you know why we don't eat cookies all the time? [etc...]
D. Yes. Can you talk one to ____ also? Do you think they want one?
Each of these is a series of short explanations along with a question for him to answer and speak his mind. If he doesn't understand I say something similar I know he can respond too.
For a 2 year old, people have remarked how well he talks/communicates.