Some tips to improve power (and hitting the weights is not one of them, in fact it is usually detrimental as it is more about muscle isolation, the opposite of a good punch which is all about coordination). put all of your weight on the side you intend to punch with, if you are orthodox and want to throw the right put all your weight on your back foot, this is "sitting down" on your punches, bend at the knees (nothing destroys punching power like standing too upright or having your weight over the wrong foot as you throw a punch). relax you shoulders (a lot of people shrug or jam up in the shoulders, this is where arm punching starts, as soon as you lean in too much or jam the shoulders you are not using the weight in your lower body. stay relaxed and hit with weight not muscle tension (getting tense slows the punch on impact turning it into a push, acceleration on impact is the key (that is why an overhand is so effective, circular momentum means it is always accelerating). i have a heaps more tips and ways to improve power but you will get sick of reading before i get sick of raving about throwing a good punch.