boys can shake his leg because it is a habite and he like like the way it feels.
A boy can also shake his legs because he is streesed out!
It feels better if he shakes his legs very fast in just in his underwear and it is good for legs.
The centrifical force between ones gluteus maximus, and music creates one revolution, aka a twerk.
You can learn by watching other people twerk, But basically its just moving you butt and hips, but you have to arch your back just a little or you will look very awkward while dancing, you need to have quick abilities with your butt, or it will look like your a girl/guy that is trying to dance like a maniac, but seriously, its harder than it looks, but easier at the same timee. (: