When I map controls for the new module, I look at the real life stick and throttle, and try to map my own as close as possible to the real thing, within my hardware limitations.
Also, I try to keep consistency within all my modules. For example most aircraft have radio button on the throttle, NWS, radar and autopilot on the stick. I always try to map those controls to the same buttons across all my modules. Makes things much more easier to remember...