Whether you do barbell curls or dumbbell curls, right at the "end" of the last rep of each set, don't let the bar(s) all the way down, keep pressure on your arms and forearms especially, they will be just bursting out of your skin (unless you are a real newbie and haven't got ANY vascularity at all)! If just starting out and no vascularity, do the above anyway, it'll start the veins on the road to break out. On dumbbell curls, do one arm at a time, starting with the 'bell and your palm facing your side, lift up, and at the same time, twist your palm and wrist to have the bell not only come up, but twist it all the way that you can go to the right (right arm), hold for 1 or so seconds AT THE TOP of your biceps peak, you get the advantage of lifting with your bicep/forearm, but the supination gives an edge to your bicep, and that wanted vascularity.