Begin with your arms shoulder width apart, and hold the dumbbells right at your sides. Make sure your palms are facing towards your hips.
Slowly bring the dumbbells toward your chest. While you are bring them up, you need to twist your wrists so that your palms are facing up with your thumbs pointing out.
By turning your wrist, you will be able to get better muscle contraction when you get to the end of the lift.
Make sure when you do get to the top of the lift, squeeze the heck out of your bicep!
While doing this work out, you must only be using your elbow joints. Keep the rest of your body as still as possible.