(In no particular order.)
When writing:
- Which pieces of content would benefit from a graphical illustration?
When editing:
- Is the tense consistent?
- Is the usage of pronouns (you, we) consistent?
- Is the use of passive voice reasonable?
- Are the sentences short enough?
- Are the references up to date?
When reviewing:
- Separate into passes (in no particular order): content, spelling+grammar, formatting, punctuation.