I'm going though this too!! My son just turned 5 in December, and I'm due in July! There have been a few instances where I whined back at him, then asked if he liked it. However, most of the time I try to use my calmest voice and ask him, "Does whining ever get you anywhere? Is there a better way to ask for what you want? Because if you asked nicely for five more minutes of play time with your frineds, I may have let you have it, but because you whined, we have to leave right now." Then, when he does remember to ask nicely, I make sure to let him know that I appreciate it when he is polite, so we can stay for five more minutes. However, there are times when it just isn't possible to give him what he asked for, and I get down on his level, give him a hug and say, "Thank you for being such a big boy and asking nicely. Unfortunately, we won't be able to stay longer because..." I have learned that if I talk to him like I would an adult, even though I sometimes have to go back and explain what some words mean, it helps cut the whining down a lot, because he doesn't hear adults whining. Good luck!!