I have a small freelance client whose site I've offered to port to D8 pro-bono as a learning exercise for myself and a friend who's learning Drupal. It'll take a number of months to do, even though architecturally it's a small site, but that's fine. My very first step was to create an initial plan on what steps we'd need to do to to plan the site build. Seeing as this list ended up being completely generic, I figured I'd share it.