rules are simple: you post a cause, and the following person posts an effect, a reason for the effect involving karma, and makes another cause.
example:
dude 1: you point at a guy
dude 2: he gets offended and punches you in the face. you had kicked a dog earlier, so this is karma.
you kick another dog
dude 3: *follows suit*
get it? okie dokie then, let's go.
you just brushed your teeth