@chilly Again, a blog post or tips or both!

thanks for the replies, although I would have expected more answers

Sorry you didnt get your answers. It has been my experience that about the only documentation about how to build a plugin, module, or component is on the joomla site, and in a few books.
There is a sample k2 plugin here on this site under extensions.
If i were starting on a module, i would grab mod_k2 content or mod_k2_tools depending on which was closer to what i want, and start with the code itself.