You are to avoid having stiff figures in your art. Unless there is a reason that serves the story. The character may be hypnotized, a zombie or a robot. Or perhaps your want to show the character is balanced and/or powerful.
Before we get to what you may normally think of as "action" I want you to consider something. Even a still figure can have an action side. You need to look for a passive and active side to every figure, even their limbs. It will help to bring your figures to life.