When doing dumbell curls, if you rotate your wrist on the way up, so that your palm faces up and almost away from you, and rotate so that your palm faces you on the way down, it will help to build a peak on your bi's. The act of turning your wrist like that helps you to get more of a contraction. I'm not sure if that's pronating or supinating. You can see what a difference it makes if you just make a motion like you are turning a key in a lock, watch what your bicep does as you do that. I agree with Louden Swain ( I still love Vision Quest) about the brachialis. They really help to accentuate great arm development. My favorite for that is seated incline dumbell curls. Keep your shoulders, elbow and wrist in line out to your side throughout the movement. I see most people sit on the incline bench and do regular dumbell curls out to the front. I think that lessens the impact on the brachialis. You do less weight if you stay strict out to the side, but it really hits the brachialis. After all, you're not in the gym to impress anyone (I'm not anyway). You're in there handling your own business and doing what you have to do. I hope you can understand what I wrote. Sometimes you just have to see something to understand it.