Sometime between six months and one year I teach my children a couple words in sign language. Simple things like "please" and "thank you" and "more" so they can communicate with me before they learn to actually speak those words. And it greatly cuts down on the amount of fussing I have to listen to on a daily basis.
William still uses his please and thank you signs a lot even though he's old enough to say the words in some recognizable form. Granted, they may not be recognizable signs to those who actually know sign language. His please has evolved into a quick side swipe across his stomach instead of the circular motion it is supposed to be. And he uses it (very politely) whenever "yes" is also an appropriate response. However, I have found that this has very dangerous side effects. For instance, when I notice that William is perched precariously on top of his overturned tractor toy that is wobbling in a worrisome manner and I ask if he wants help getting down. In that type of situation I would prefer he didn't take away one of his hands, that is barely keeping him from toppling head first onto the cement, in order to say "please".
Funny, I don't recall having this problem with my safety conscious daughter who, as a toddler, hardly climbed on anything.