I remind my kids to think: does the apostrophe work as a band-aid or a lasso. If it doesn't, it's not needed.
I don't claim the band-aid story. My students gave it to me, but it sure is clever! They told me the apostrophe is like the band-aid in contractions. Since the two words were squashed into one, some of the letters popped out, and the band-aid is needed to heal the spot where the letters popped out. Of course, this story has evolved, and now I tell them certain letters were "surgically removed." They really enjoy saying "surgically removed," so I enhance the story to keep their attention. I also mention that the surgery doesn't hurt at all, in fact, it tickles! If you listen closely, you can hear the letters giggling.
I do claim the lasso story as my own. When teaching possessives, I make sure the kids know the word "possess" means to own or have something. I'll get into stories of rodeos, telling them how cowboys throw their lasso and claim their cattle. I show them pictures I've googled of cowboys and lassos. In a possessive, the noun with the 's owns the following item. (or nearby, in the case of an adjective) I even get into turning the apostrophe into a lasso and circling the next word. They practice this on their whiteboards (I'm a whiteboard fanatic!) and love to draw the lassos.
Naturally, if the word they're thinking about doesn't need a band-aid or a lasso, they shouldn't be using an apostrophe.
We know how these little stories help the children remember. After 35+ years of teaching, I have lots of little stories and "tricks up my sleeve." Recent brain research shows us these little stories help make the connections in the brain so the children can build their knowledge. Plus, it's fun!
One of my favorite resources has this Band-Aid/ Lasso theme. It has these two stories to help the children remember when to use apostrophes, and has 4 activities to practice contractions, plurals, and possessives.
or you can try the digital Boom Learning version HERE: