L.H.
I used to pat my son's mouth to make it sound like a funny "wawa" noise, then we'd both break down laughing. Then I'd suggest we sing and we'd start singing the alphabet song. It worked so good that he stopped screaming all together and changed over to singing various song, especially when we'd stand in a line at the cash register. The more people would smile and comment, the more he'd sing and boy, was it cute.