Nice guide, just one small issue with your eighth point.

[quote=@Gunther]
Also, when showing possession, please do not forget the apostrophe. "This car is hers" should read, "This car is her's."[/quote]

The example used here is actually grammatically incorrect. Hers is the possessive of her as opposed to her's, this is because of how pronouns function differently when it comes to possession and never use apostrophes. Same is true for its, ours, yours and theirs.