I organized all the information contained in the thread "Against Knockout" that has a big and valuable amount of information about Knockouts and how to avoid it. Hopefully this will help.
What is a knockout?
Is when the head rotates sharply causing the brain to bounce inside the skull. This trauma to the brain stimulates a big number of neurotransmitters to fire at the same time, overloading the Central Nervous System and sending it into a temporary state of paralysis.
There are three degrees manifestations of this trauma:
The typical knockout that results in loss of consciousness, and no memory about what just happened.
The "flash", which is a rapid loss of consciousness.
The Stunning, when consciousness is maintained despite distorted proprioception, visual fields and auditory processing.
Other ways of getting Knockedout?
Getting hit in the Carotid Sinus (or Carotid Bulb), a Pressure Valve located on the side of the neck which senses blood pressure. When you get hit there the body thinks that the blood pressure is critically high and shuts down.
What are the most vulnerable points?
The sides of the Chin and where the Jaw is attached to the skull are the most vulnerable points.
What to do.
You cant strengthen your chin. You are born with Steel Jaws or you are f*ckd, and better have good defense skills to compensate.
Always keep your
-Eyes on the Opponent
Watch the blows. Never get caught unaware. Most knockout punches are the ones you dont see coming.
Strengthening the Neck muscles can be of some help but should not be a priority.
Improve your footwork.
Work your Upper body movements.
Lack of hydration when cutting weight can be an aggravating factor. With less fluids inside the skull the brain hits the wall harder.
Avoid having extremely low body fat because it is not only prejudicial to the brain but also to all internal organs since fat has a cushioning effect.
Have good conditioning. This can be decisive.
You can train your jaw by chewing thick Gum or using a device that uses weights to force you keep your jaws clenched.
Dont be punch shy. If you freak out and freeze when receiving blows you are f*cked. Having a sparring partner can really help with this one.
As you can see once again the ultimate factor is genetics but there is plenty you can do.
Thanks to everyone who contributed in the original thread + wikipedia.