Just got home from the second part of "Tactical Pistol I". We mostly concentrated on using cover and movement, and LOTS of drills on clearing malfunctions. Always well worth spending time training, and even though I had the course a couple of years ago, I picked up some tips, and was told by both instructors that I've improved tremendously since I took my first tentative steps at serious training. Mostly, I don't get flustered if something goes not-to-plan, and just keep my wits about me and finish the drill. 8 out of the ten in class were very good, and the other two guys were beginners, but they improved a whole big bunch since last week.
I'm going to take "Tactical Shotgun I" in a couple of weeks, another course I had about 18 months ago. Since I don't take my 870 to the range very much, it'll be a really good refresher for me. The important things I learned before were proper aiming, and how to keep the thing running. Too many people have the impression that a 12 gauge shotgun sends an "Atomic Cone-Of-Death" at anything it's pointed at, and that's just not true. A shotgun has to be AIMED just as much as any other firearm, and at close ranges the pattern doesn't spread out nearly as much as most people think.
It also has a voracious appetite for shells, and learning how to reload it under stress is very important. Even with a magazine extension, you basically have a "Five Shooter" or "Six Shooter", and there's no speedloader or magazine to swap out in a hurry. Nope, you gotta stuff those shells in one-at-a-time, and learning how to do it efficiently is vitally important.