Argghhh! Gunfight Rulez. Just a few of my favorites, but it is worth looking at them all. Most apply to any self-defense situation you may encounter.
USMC Rules For Gunfighting During WarRule 24 is the old saw about handguns that are smaller than .45 caliber (or rather always use a gun that has a caliber starting with .4). For the military - limited to FMJ (that's Full Metal Jacket for you non-gunnies) by the Hague Accords of 1899 and 1907 - this rule probably makes sense. For those of us who can use semi-jacketed hollow-points, somewhat smaller calibers can be very effective. [h/t Alphecca]
1. Bring a gun. Preferably, bring at least two guns. Bring all of your friends who have guns.
12. Have a plan.
13. Have a back-up plan, because the first one won't work.
16. Don't drop your guard.
17. Always tactical load and threat scan 360 degrees.
21. Be polite. Be professional. But have a plan to kill everyone you meet.