How can i break my kid of a bad habit?

i used to do that, but stopped when i started to play musical instruments,and i draw and write and stuff. my fingers were bored i guess, twiddling is a way to control my hyperness. perhaps you should put him in some sort of lessons.

First try to identify the specific times he is doing it. It is likely while watching TV or doing something "mindless." Next, during those times, give him a koosh ball, piece of curling ribbon, stress ball, synthetic rabbit foot, or something else to play with. Eventually he will become conscious of the behavior and wean himself off the replacement. You can also try videotaping him twiddling his thumbs and show him how it looks. He might decide for himself that he wants to quit.