This episode of the Principles of Design is all about dynamic compositions. The path your viewers' eyes follow though a painting is no accident, so make sure you're using it to your advantage! In truth, each Principle of Design is intended to help guide the viewer's eye, but "motion" is especially effective at this goal. Additionally, if you've been following the series I'm sad to report that the orcs are sitting this one out.
And make sure not to miss the other videos in the Principles of Design Series!