Having now been to Japan twice, I have always had a curiosity in the ritual of bowing, a courtesy which is entrenched in Japanese society.
I found this Youtube video which threw some light on the practice.
I have to admit that I have never bowed to greeters in stores and shopping precincts, and have always been careful on to bow to the same level as they did to me, so as to avoid them feeling they need to bow again to match mine, and so on!