Well, I can sit still as long as my hands are constantly moving. If I'm busy writing then either I'm adjusting getting comfortable on the chair or moving my legs constantly. If the chair swivels then I don't move my hands or legs, just the chair.

If I'm sitting in a social setting that I'm feeling at ease with, I am usually playing with my hair or tapping the table. If I'm not terribly comfortable, then I really feel the need to stand up and move around.