to get back to the wild little boy in the hospital, who was the subject of the beginning of this thread -

I once knew the dad of an obstreperous two-year old. When she was getting out of line he didn't say something vague like "Calm down" or "Knock it off!"

He'd say, "That's too loud, Holly." That way she knew what he wanted and who he was talking to.

Since then I have also learned that it is much easier on everyone if you tell what you want rather than tell the child what you object to. For example, instead of saying, "Don't climb on the dining room table," say "You may play on the floor or on the couch." Naturally there are times when this won't work, but as a general principle, it makes sense.