Apostrophes and how to use them

I've been teaching writing as part of a communication class for a while, and one of the things I notice is the difficulty students have with apostrophes and possessive pronouns. Now, I realize learning the rules for these things can be tedious, but flawless writing is important. I also know that students learn different ways. So here is a nice visual lesson in correct use of apostrophes. Does that make it easier to understand? I'll let you decide whether it's a good explanation of a concept that is often seen in students' work. (Did I get it right the three times I used an apostrophe in that sentence?)