I am not really inclined to believe that there is any real "key" to winning a gunfight. There are measures you can take to help you be prepared for a gunfight such as training/skill/knowlege/practice. The skills aquired from such things can lend you some specific advantages but does not mean that you are going to win over someone with less knowledge and training. All thing being exactly equal, yes.. I believe that the best trained, most skilled, best equiped person is very likely to win each time... but what gunfights are exactly equal?
Winning can depends on advantage:
Training is an advantage
Skill is an advantage
Better Equipment is an advantage
Numbers are an advantage
Position is an advantage
and so on and so on.
When you add all this up, is it enough to overcome the enemies advantages? It could depend on the actual worth you assign to each advantage plus a % of blind chance. yep, blind chance..
I believe that its always best to be well trained, well practiced and well equipped. I just dont necessarily believe that winning a gunfight will ever be as easy and written list of one - two - threes.
Life is a web woven by necessity and chance...