Mirrors on the ceiling...why am I not surprised?
(1) Face the mirror...give the number, signal, and consequence (verbal call too, if you're alone, or not afraid of looking like a freak in front of your family). Make sure the signs are in that "window" in front of your face. Make sure you're standing straight, and that your voice is clear.
(2) Do the same thing, only turn 90 degrees, so you can see a side view (are you hunched over, etc).