Things I've found useful:

* Use a platform where it's very easy for people to give feedback. I've used Google Docs and Quip.

* Write documents when there's real disagreement about how something should work.

* Ask specific people for feedback on your documents.

* Ask other people to write things, read what they write, and leave good comments.

* Have a regularly scheduled meeting for reviewing team documents to get feedback. Anyone can sign up with a doc they want reviewed.