C.O.
We have not really had a bigh problem with this. I wish I had some good advice...but I do see responses that look very hopeful! When Alyssa (2-1/2 yrs) does get whiny we just tell her we can not understand her and that she has to speak clearly. Usually this will work and like I saw on the response page, we always praise her for asking so that we can understand her. I think this also has helped her to lear to say please, thank you, you're welcome and excuse me especially when she wants something!
Good luck, C..