Comma Rule 3 probably doesn’t sound like fun, but it is. It goes by some technical and rather boring names (appositive, non-restrictive clause, interrupter). The basic idea, though, is simple: Use a pair of commas when your voice drops. One comma takes your voice down, and another brings your voice back up.
Here’s a familiar example from Mission Impossible:
Your Mission, should you choose to accept it, is to intercept the enemy plane. COMMA RULE 3
Easy, isn’t it?
But wait! I’ve got an even better example for you. Click on the link for Superman!, and you’ll be able to hear a wonderful example of Comma Rule 3.
Notice how the announcer’s voice goes down at the word who (comma) and comes up again at newspaper (comma). Turn on your speakers and listen for those two commas – it’s fun!
I never used any grammatical terminology when I taught Comma Rule 3 to my own students – it just intimidated them. Instead we played with voice-drop/rise sentences (which I always called “Superman” sentences), and students caught on quickly.
Here are some examples. I’ve marked the non-restrictive clause – sorry, the “Superman” – in red. But I’m betting you won’t need any extra help with these. (For best results, read them aloud, emphasizing the change in your voice):
Superman, disguised as Clark Kent, fights a never-ending battle for the American way. COMMA RULE 3
Because we’ll be visiting Margaret, who’s my favorite cousin, I’m really looking forward to our trip to Maine. COMMA RULE 3
Creating PowerPoint presentations, which I thought would be difficult, turned out to be easy. COMMA RULE 3
Lucille Ball, one of the funniest women ever, credited Desi Arnaz with much of her success. COMMA RULE 3
You’ll find that often, but not always, the words who or which appear at the beginning of the interrupter. Try inventing some “Superman” sentences of your own!