ACTION LINE

Always keep the line-of-action simple. I think a gesture, in order to have any kind of punch to it, needs to be based on either a straight line, a curve, or an "S" curve. Those three types of lines have direction and force to them. Anything else, like a zigzag or a more complicated series of curves, loses its ability to convey an action or direction."
"If you push a line of action too far, or in the wrong way, you can sacrifice the structure of what's underneath and you're left with something that feels like it's made out of jelly with no skeleton - that's not good.