My personal favorite of the list --
20. The faster you finish the fight, the less shot you will get.
But I also like what Lizette said above -
RELOAD AT THE FIRST TACTICAL PAUSE.
BEFORE YOU QUIT THE FIGHT, MAKE SURE THE FIGHT'S OVER.
I conceal carry and always carry a spare magazine when I leave the house. There can be no worse feeling than running out of ammo in a firefight. True, most street gunfights last 6 seconds or less and it's over. But I'm a firm believer in planning ahead - what if they come back? At least I know I'll have a full magazine and prepared if they do.