A recent internal Commercial Progression project allowed us the opportunity to set up a Drupal 8 site and get REST working on it. In the process, and by merit of the stack being new with the documentation catching up, I learned a few tricks that might be useful for enterprising developers out there.
1. POST-ing entities is to a different path than the REST UI says
If you install the REST UI module and enable an endpoint, you'll see a screen like: