Partly compiled and truncated from Gwern.net: Writing Checklist and Software For Writers: Tools To Improve Your Writing.
choose a good title
check for broken links, archive if necessary
add footnotes for academic papers and books
make sure formatting is correct and looks good
add links to other relevant posts I’ve written.
add keywords, tags and meta summary
add a social image
bold the important parts.
check the quality of external links (make sure the domain isn't full of trash)
add more relevant examples if possible, especially personal ones.
humanize the writing.
remove unoriginal metaphors or examples.
remove hedged phrases, weasel words.
switch passive phrases to active.
remove any foreign phrases, scientific words, or jargon that aren’t necessary.
read out loud and check for flow.
remove any criticism of other people.
search for “ly” words and remove them.
carefully consider and justify any use of exclamation marks, semi-colons and parenthesis
remove commas that aren't necessary (e.g. before "too" at the end of a sentence)
strip needless words.
check reading level.
have other people read it and get their reaction.