at my dojo we bow before we enter, before we start, during training, after training, and as we leave. when we have drinks break we bow and if we approach any black belt of 3rd shodan or higher we bow, say oss and continue with whatever. we also bow to our partners when doing kumite. it gets a bit repetivie but i don't mind as it stretches my back. i actually hang out with a couple of the black belts from my dojo and we greet eachother in the normal way.