An excellent rule to follow there, Tartan.
Personally, it's one I was familiar with long long ago, and for some reason tend to ignore in most of my work.
Glad to see I'm not the only one revisiting some basics.
And BTW, I like this image, too.
Good texturing, love the smokey effect, and yes, the focal points here keep me moving around the scene, yet for some reason I return time and time again to the babe's focal points.
Good Job.