2. Anything worth shooting is worth shooting twice. Ammunition is cheap - life is expensive. If you shoot inside, buckshot is your friend. A new wall is cheap - funerals are expensive
This one translates well into: Never believe something, know it. In other words: Overkill is just right. An enemy that has been sawn in half by your; gun fire, laser fire, magic, animal tusks or sword is probably not going to come after you again.
4. If your shooting stance is good, you're probably not moving fast enough or using cover correctly.
This one has two major forks to its point for writers, and those unfamiliar with guns:
- If your enemy is moving at your slowly enough, and without any ranged weapons, that you can get into the picture perfect stance seen in target competitions and bad movies, it is either a) not very dangerous or b) it's confident enough that you should be taking the time to run away.
- Standing in that wonderful range posture makes you a delightful target for anyone (the enemy you see or the one(s) you don't.
While blowing away all your ammo in the first five seconds isn't great tactics either, waiting for the perfect shot you have to be realistic and think of the possibility of losing your gun. This is most important if you or your character is small, weak, hurt, or your enemy is that strong.
16. Don't drop your guard.
This seems to be what makes the plot in horror movies (what little there is) work, but you can rarely get away with it in good books.
20. The faster you finish the fight, the less shot you will get.
Obviously this applies to all weapons, and magic, and hand to hand as well.
24. Do not attend a gunfight with a handgun, the caliber of which does not start with anything smaller than "4".
While the "caliber wars" will rage eternal, you'll note that many police departments carry .40 or .45, some will go with a 9mm simply because it moves faster and in theory has both takedown power and leaves the chance of survival for the person hit.
27. Regardless of whether justified of not, you will feel sad about killing another human being. It is better to be sad than to be room temperature.
The second sentence of this one is rather more important than the first. I hope I never have to kill anyone, but if the choice is me and mine or some schmuck that has actually made me want to kill them, it'd be unwise to bet on me feeling too bad about surviving.