Just thought I'd post about something that works sometimes when Boo says "no." I tell him Boo can say "yes mommy". Sometimes he still says no. But there's quite a few times where he will say "yes mommy" and do whatever it is I'm asking him to do.
I learned this approach years ago as an infant teacher and it is much more effective overall than the familiar line "Don't you tell mommy no." I think it's because it tells the child the exact response and behavior you're looking for instead of just telling them what you don't want them to do. Hmmmm...that sounds familiar.
Anyways, it works for me enough of the time that I thought I'd share.