Sounds stupid, but it actually works. As soon as my co-workers learned that there was a possibility, however remote, that they would be rapped in the forehead if they continued to ignore the basic rules of apostrophe usage, things improved dramatically. One, though, became so fearful that he stopped using apostrophes altogether, which didn't really solve the problem. This was a guy who would say "Me and him were at the meeting", so he was obviously a special case. The thing about apostrophes, though, is that by the time you get to be an adult, you've been exposed to the simple rules of usage dozens, if not hundreds, of times. To get them wrong would require a willful act of rebellion, you'd think. And yet you see glaring errors on signs, in newspaper headlines, in books, everywhere. I can even detect them in speech, if I'm really focusing.