A friend of mine wrote a short ebook [1] on the subject, and I [2] thought it was excellent. He's currently a lead technical writer at Palantir.

[1] https://www.amazon.com/Modern-Technical-Writing-Introduction...

[2] I wrote a lot of Fluentd's documentation in its early days http://www.fluentd.org/

Um... not much has changed in the technical writing world. There's a few better tools for using images/video, but nothing really that great (someone go build this please!).

The things expressed in the article are still pretty valid. Except for the first one (I don't like cutsy documentation), the rest are solid starting points.

The biggest one for me is to tell people what to do. Don't ask or talk in the passive voice.