Start light until you master the form. Hold a dumbbell in each hand with your arm bent, as in the top of a biceps curl, so your palms are facing you. Now, instead of pushing straight up, spread your arms to each side laterally, then press your arms up and twist your hands so your palms face forwards. For full range of motion, finish by pushing your head forwards and reaching as high as you can so your biceps are close to your ears.