I am not very concerned with the definitions and proper use in generic English language usage, as in the below quote from English Club. That is not the nature of my question...
What I am asking about is when to NOT (or NOT to)use them in situations where conversationally you would. Technical and academic writing avoid them, but conversationally we seldom say, "What is up?"
I guess I'm fine with the 'it depends', but what are your thoughts on fiction vs. non-fiction, and 1st, 2nd and 3rd person?
If the possessive noun is singular, always add an apostrophe + s. If the possessive noun does not end in -s (in its written form), always add an apostrophe + s. If the possessive noun is plural and ends in -s (and this is a characteristic feature of the large majority of plural nouns), just add an apostrophe.
[h=3]A Tip for the Possessive Apostrophe - English Club[/h]https://www.englishclub.com/esl-articles/possessive-apostrophe.htm