Follow Material Design's writing principles whenever possible. This applies anywhere we communicate with words, such as microcopy for apps, articles for this playbook, and pull request messages.
The guide has some very obvious guidelines, but there are a few that are worth paying extra attention to. Here are a few:
Write in the present tense. Avoid using the future tense to describe the way a product always acts.
Begin with the objective. Start sentences and paragraphs with a goal. (This is explained further in Progressive disclosure.)
Write for all reading levels. Short common words are better than longer ones (eg, "Turn on" instead of "Enable").
Material Design also endorses a few other guidelines.