From a martial arts perspective where we train to kill, knocking out is less likely than other things. However, there are many, many ways to render a person unconscious. Most that come from blows/strikes are not sure-fire ways to do so.
Generally, at the base of the skull where the medula oblongata is is a good way to knock a person out. You see it many times in movies with horrible karate chops. That would almost never work, from experience. It takes a nukite (thrust of the fingers) or a very accurate punch to the base of the skull at the back of the neck to come close.
The less prepared the body is for something, the more likely it will work. In its relaxed state, sudden impact whiplashes more. Your body is forced to move with the flow. However, in a fight situation generally the body is a bit more tense and able to resist foreseeable impact.
Most sure-fire ways to make something lose consciousness result from strangulation or choking techniques. I'm not sure which is which, honestly, but one we tend to define as "cutting off air flow" and the other as "cutting off blood flow" and there are about.... seven thousand to infinity ways to do this. Some attack the arteries, others attack the diaphragm, what have you. Generally, these holds are applied not to truly kill a person outright from choking, but to do one of a few things, such as: A) make them easier to tie up and transport as a prisoner, B) to weaken them so that you can kill them easier, C) to give you a brief rest (most chokes are applied from grappling, as most fights end up there, and side-mount is such a lazy-man's position).
I can't say I'm a normal person and I've been hit in the head with baseball bats, dense oaken staffs, fists, brass knuckles, and the like. I've never lost consciousness, but I have blacked out standing before. That came with a strike near my temple, I think.
Also note there's a huge different between a concussion and a contusion. Contusions can lead to comatose, but can essentially happen in similar fashions.
How do normal people react in fights, though? Per experience, most Americans tend to take a boxing approach with wide haymaker punches. Usually when that fails, they then go for a naive wrestling approach and then go for the legs to take you down. I saw a man go out after falling from such a thing onto pavement, but it was very brief.