When I was at Lafayette Elementary School in West Seattle, they taught penmanship, otherwise know as cursive writing, in the fourth grade. Our teacher, Dorothy, was constantly admonishing us to hold our hand and forearm up and not rest them on the table. This was virtually impossible for me. I did manage to learn to write the letters in cursive and I can write legibly in cursive, mostly, now, but it's not what you would call fluid or elegant. Passable, I suppose.
I never figured out what Dorothy was on about until I saw the movie Plein Soleil (above, aka The Talented Mr. Ripley) as part of a French film class in college. In the movie Tom Ripley practices forging his target's signature by writing it in really big letters on the wall. He is using his whole arm to do this. His hand and wrist are a rigid extension of his forearm. This is what my teacher was trying to tell us. I have tried practicing writing using this technique but it's a hard habit to develop. If I had been trying to write great big letters on the blackboard back in elementary school, I might have had more success, but trying to develop fine motor control of my whole arm was, at that point, beyond me.
There might be a video out there that demonstrates this technique, but I have been unable to find one.
Inspired by Bayou Renaissance Man
Update January 2018 replaced missing video.