So Rocky Marciano, Earnie shavers, Tyson, Smokin Joe, George Foreman, Ruddock, Morrison etc are trying to punch for maximum power. How are they doing this? Guys like Ali, tend to prioritize footwork over maximum punching power, as far as I know.
They practice. A lot. Dude what's with the threads? I suggest you go to http://www.expertboxing.com/ and look at the tutorials. They have all the basics covered.
Guys who are born with punching power tend to practice more on knocking people out, and get better and better at it. Guys with limited power need to work more on other things.