Today I have been following the OS Training 'How to Develop Drupal 8 Modules' course.
So far, it's clear and well laid out, and it is working. Im understanding it and the exercises function. So, far, far better than what as an apprenticeship class we have been attempting to follow for the past month or so at github.com/OpenDrupal/opendrupal-drupal-module-development
So go here instead: ostraining.com/class/d8-dev/ It is much better.