Dont know if you cover this or not, but we do...
Show the class the differences in .380,9x18,9mm,9Mag, and explain that the ammo MUST say the same thing as what is printed on the gun.
Some people just assume or perhaps are incorrectly told that a 9x18 will function just fine in a 9mm, when in fact it wont. We have had students bring 380 ammo for their 9mm's, .357 ammo for their .38's and .45 LONG ammo for their .45's.
We have once fired cases glued to a board that we use as a training aid by passing it around for everyone to see. We also have various types of bullets glued to a board.
I once intervened at the range when I saw an older gentelmen banging his slide on the table to get it to close. What he had done was load a .380 cartidge into a 9mm, and the slide only lacked about a 1/16 of an inch of closing up. Had he managed to fully seat the 9mm and fire the gun, you can imagine what would have happended to him and the guy at the next table standing beside him.
In dealing with law enforcement, tell them that is is NOT a good idea to show the officer the gun unless he requests to see it. At a "shoot/dont shoot" class, taken by deputys here, one of the scenarious was that of an elderly woman being stopped and immediatley showing the officer the gun that her son in law got her for protection.Even though it was totally innocent, she broke all of the common sense rules and pointed it at the officer,finger on the trigger and wanted to hand it to him form the window.
At least half of the officers "fired" at her. Upon review, the true intent of the woman was seen, unfortunatley, it was misinterpreted by the officers way too many times.
Also, altough I've seen it happen here on numerous occasions, the local resturaunt parking lot is not the place to show off ones new piece.
I once went on a call about two subjects "brandishing " weapons at each other, I was less than a block away went I got the call. Other units were called, we figured a fight was about to take place. What I encountered were two friends comparing the difference between a HK fullsize and the Compact versionand they were completely unaware of the funny looks they were getting from some of the people entering the restraunt. Although no big deal to most in this state, it was a couple from a notriously antigun state up north that was passing though and decided it was time to eat. After a breif discussion with the suspects and the complainants, all was well. However, in a big city, high crime area, it could have gotten somewhat ugly.
These are just a few things that we have incorporated into our classes over time. Maybe they'll help.