Didnt read the whole thread so hope I wont repeat anything that has been already said.
I practice MMA and fight at amateur level (minor challenges nothing serious) so first of all I wanted to say that even before the technical skills, what a guy needs to improve his chances of walking away unharmed is to avoid the confrontation to begin with.
If thats not possible technical skills are gonna help as long as you are in great shape in terms of mental sharpness, stamina and strenght.
Forget about that kung fu stuff you see in jackie chan movies, big strong guys have an edge and no matter how good your tech is, you aint gonna knock a guy down if you are 50kg skinny girly boy...same thing if you thrown a couple of punches and run out of breath.
Now regarding the techniques, clearly as someone said early striking is the best option since it allows you keep your distance and be effective while any non trained opponent wont be as good in terms of hitting and dodging hits, many will even throw themselves at you rugby style.
Few well inflicted punches are enough to disable your opponent or simply push him to stop the confrontation, in that case allow the guy to save his ego and make it seems like its a shared decision.
If you happen to get chest to chest then you need to wrestle and control the way you will fall, needless to say you want to stay up and want him to be down...that way you can strike, grapple or simply stand up and run away.
If you are unlucky enough to have a fist fight with someone who knows some boxing or worse yet he does better that you do then great wrestling skills can save you, again once on the ground he will panic and possibly will be willing to cease fighting.
I had fights with guys coming from many years of boxing that were clearly faster then me and whos fists and space control were impressive compared to mine...the reason why I didnt get knocked down was simply that my wrestling and ground£ skills are good enough while other times I saw great wrestlers being struck from distance only to have their opponent escape from any of their take down attempt.
In my experience techniques, mental sharpness and physical shape are 3 sides of a triangle where they should all present for your own safety.
Ps. no sport does nteach illegal moves yet expect them to happen in a street fight.
The best skills in the world wont help if you are too scared to move or have no gas to fight.
So learn and practice, better yet have minor fights to test your nerves and measure your limits.