IMO, the two most important things are:

1. Put role="main" on the element that contains the main content of the page.

2. Make sure your headings are semantic (h1, h2, etc.), not just visual (e.g. divs or paragraphs with certain font sizes).

The rest is nice, but much less important IMO.

Don't get me wrong, I'm glad to see an article on this subject on the front page, and it's very thorough. I just thought a very brief summary of the essentials might be helpful.