Selected answers from the Dumb SEO Questions G+ community.
Dave Elliott: step 1) do keyword research to find the more popular keywords related to your subject matter and use these in titles and headings and if given a linguistic choice use the more popular keywords rather than the less within the content
step 2) write naturally about the subject
step 3) Don`t care about keyword density
step 4) go to the pub
Neil Cheesman: Keyword density? Amount of text on webpage?
Type "is it Christmas" into Google - website at number 1 - has one word on it (I think it is text although could be script) :) https://isitchristmas.com/
Alan Bleiweiss: Keyword density is irrelevant to SEO until it becomes keyword stuffing.