It's your day to master tricky possessives

I've been reading more Indie authors these days, now that I'm one myself. One error I keep seeing is confusion about its/it's, who's/whose, etc. It seemed that a quick primer would be useful to lots of folks.

The rule here is very simple. Put it on an index card if you must.

Simple pronouns DO NOT take apostrophes in their possessive form. 
Pronouns morph into new words.
If there is ownership involved, no apostrophe. Got it?

Here is a quick run-down of the pronouns and their possessive forms:

I love MY sweater. It is MINE.

YOU love YOUR sweater. It is YOURS.

HE loves HIS sweater. It is HIS.

SHE loves HER sweater. It is HERS.

IT displays ITS sweaters. They are ITS.

WE love OUR sweaters. They are OURS.

YOU (plural, like y'all) love YOUR sweaters. They are YOURS.

THEY love THEIR sweaters. The sweaters are THEIRS.

WHO loves WHOSE sweaters? The sweaters are WHOSE?

These stand-ins for nouns take apostrophes only as contractions--when paired with a truncated verb (who's means who is, who was, or who has). I'll give more detailed descriptions in a separate post.

Compound pronouns behave like nouns. They DO use an apostrophe in the possessive form:
anybody's picture
anyone's coat
everybody's problem
everyone's favorite
nobody's fool
no one's girl
somebody's pet
someone's present

Do possessive pronouns trip you up?