I will teach you daniel son. One of the keys to punching very hard is focus. You have to be into it, enthusiasm. You have to concentrate on your muscles when you punch, and make adjustments acordingley. Then start hitting the bag focusing on form while paying close attention to what muscles come into play. Forget about speed (if you do not have much power). Then you have to hit the heavy bag ALOT. But when you punch you have to use BOTH hands, pulling one hand back at the same time as you punch with the other, because the pulling back of your other hand increases power. Do straight left and rights on the bag about ten or so punches and every time you hit the last four left right left right or right left right left put your max power into those last punches. Remember that while you do the first six punches you have to perfect your form and the distance that you are from the bag, putting your self in what should be optimal distance from the bag, Build up your power as you go through the ten or so punches, for eg, after you have built up some power you should practice punching harder after each punch in the combo i mentioned earlier. So you will build up power, concentrating on balance, form, distance, and wrist positioning, all while you do the ten or so punches like i said make sure that you build up and set up with the first four or five punched, THEN put the power into the last couple of punches, and work at it every day, in 2 months your power should increae alot.