Now if you can make them respect your power, feinting will become so much easier. Feints work best if you make them react, and all it takes for them is good punch or two to know what you're about. There is lot's of different feints, you can feint with your hands, shoulders, knees, even your eyes if you know that's what they're looking for. The best thing when it comes down to it is to make them expect one thing, then you feint to get them to commit/hesitate, and then you Bam you hit them where they don't expect it. There's a lot more to it, if you can get a guy to buy your feints, then you can set nice little surprises for them.

Heres another thing I should add. Although strength is important, power is more about transfering weight from one side to another, more than it is muscles. If you dead serious about becoming a powerful puncher, you'll spend a great deal of time to practice shifting your weight during your footwork so not only will you be able to punch hard, you'll be in a better position to do so.