I have seen a number of different customs of when people bow or sway or bob or whatnot during Kaddish. Some of the people I have witnessed have been very knowledgeable, and I assume they weren't just falsely copying what they saw someone else do.
What are the various minhagim and where do they come from? Does it differ for different kaddishes (e.g. mourners vs. chazzan's or half vs. full)?