You need to understand why, why not, how, how not, and you need to acquire good habits.
Many Martial Arts have standardized traditional form of Kata, or execution of mostly strikes and defenses in the air to preserve the proper form of their techniques.
However, rarely these strikes get tested on their effectiveness and therefore students acquire false confidence that a strike or a kick would stop an assailant in a real confrontation.
Some systems includes brick breaking and wood breaking to test the force speed and accuracy of strikes and kicks where the object to be cut is either supported on a base or held in various methods by training partners, or held loose.
None however mimics the head position and mobility of a boxer while shadow boxing.
This method of training causes a generations effect of distraction from the purpose of training, and instead of using breaking methods to test realistic force in motion to stop an assailant, it becomes a sports competition in breaking boards and bricks.
Many Karatekas, find in street confrontation, that the traditional practice of hand strikes to the body, and most of the times never allowed to hit the opponents face, now stop short at least an inch before the opponent’s face due to honing of good safety habits but bad self defense habits.
As for kicks that are allowed in many styles to hit in full contact to the opponent’s body, but only rarely cause a knock out in competitions since the techniques was really not systematic or based on any reasonable thought considering all its aspect.
At the same time many people that train in boxing gyms but not competitively, never get a change to feel what a KO supposed to be, and even if they do only very few have a motor memory that enables them to repeat the same action and get the same results over and over.
This is spared to boxing champion and is attributed to hard training but probably to a good motor memory as well.
Usually an ability to produce a Knock out Punch comes from extensive gym or street fighting experience. Very few are the fighters that have the inner gut feeling that they are going to Knock someone with a combination of strikes or a single punch.
Killing techniques with bare hands, were probably only tested in real life scenarios where a defender had to do the best he could to save his life and in military settings where it was used as last resort.
But not much in a lab setting where someone could really break down the formula and ingredients for a successful workable strike considering that it is executed against another human being that is moving rapidly to protect himself.
So basically when you learn how to kick and punch you need to ask yourself the following questions:
What guarantees that this is the desirable method of training to a achieve a knock out punch
How long would it take me to be certain that I poses the ability to knock someone one with a single punch or even with a combinations of attacks, and what makes that first or last punch a Knock Out punch.
How do I connect all the dots to come to a conclusion that I do have this capacity and not that I just train under a reputable Instructor that I think has the ability to Knock someone out in one punch, or that have a track of proven record to his ability to Knock Someone out in a single punch.
After all, self defense scenario is not a boxing match, and is not a Jujitsu match, nor a trained assassin Ninja execution. It is a split second of reaction to surprised slash of a blade, or a bombardment of fist strikes with a knuckle guard or without.
It is a knife stab threat around the corner, or a pistol point for your wallet, or other liberties. You need something that works in that environment…
So what works better? Just keep hitting until you see a favorable result?
Train and Train and Train, until you get that magic KO punch?
More Cardio? Heavier Punching Bag? Power lifts? Run more miles than Rocky Balboa? Get KOed more than he did? Jump rope more than any boxer? Dedicate your life into boxing and Martial Arts?
First of all you need to develop an ability to see the whole pictures. If you are missing one part of the picture, all your training in mastery of the other components would not help you, since if one vital screw is missing the machine can collapse.
You need to ask yourself comparative questions. Mostly to concentrate what is the ratio of success in an organization to provide self defense skills to average people like you. How do you measure that?
Why are you sitting in a self defense class? To hear about something you already assumed? To learn something usefull?
You need to see the whole program of the training and understand the logic of it and look for any holes in the fence of the theory behind it. It has to make sense to you on all aspects, and you need to compare it to anything else available in the market. True is that most people that teach some form of self defense lack the ability to explain why, but if they cannot, you need to be able to explain it to yourself.
Otherwise you are just a consumer that will buy anything based on others recommendation with a blind trust of people you know. But remember it could be your life on the line.
The founder of Israeli Defense Forces Krav Maga, and also the Watered Down Civilian Dojo Version of it, Imrich Lichtenfeld had said that in a fight every second that passed your life is at danger. So to eliminate that danger, the easiest solution is to eliminate your opponent. So you really do not want to fight but rather to eliminate the danger as quickly as possible.
Of course you need to do your homework and find out all the legal consequences, but more important why learn self defense methods if they will not be successful most of the times when you need them? After all you live once, and why should anyone take this opportunity away from you. Well if you got killed you would not have the luxury to think it over again….