A short lesson on the apostrophe

Something has been really bothering me since third period today: the usage of grammar. I am not a grammar nazi, I'm a usage nazi.
In third period, I (not meaning any harm to come upon the teacher) suggested that he change his usage of his possessive name. He had written on the board "A****s' Awesome Activity" (the middle letters of the name have been deleted for both his and my safety). I told him that it would be correct to have A****s's, and not the way he had it. He graciously changed it after much debate from the class.
After this lovely anecdote, I ask a simple question, "Why do we spend so much time in English classes throughout our schooling, yet not seem to manage to use grammar correctly?"
I don't mean for this to sound like a lecture, but it bothers me. Let me just tell you all just one tip to not make yourself look like an idiot to any grammar savvy usage freak.

DON'T USE THE PUNCTUATION MARK IF YOU DON'T KNOW HOW TO USE IT CORRECTLY.

Now that I've had my two-bits, I feel obligated to follow up with a description of why I offer this advice. I could explain, but I'd rather show with examples of what not to do.
It is not Jones' it's Jones's. When you're making a last name plural (and it ends in "s") it's like so, Joneses. An apostrophe is used to signify possession or to signify letters that are taken out of the word (as in contractions).
That's it for my rant...join me next time for the correct usage of who and whom.

-Russell Lowe