1) Lie on a flat bench and hold a pair of dumbbells above your head with your palms facing each other. Your head needs to be slightly off the end of the bench. Keep your arms at shoulder width and your elbows slightly bend.
2) Inhale and slowly lower the dumbbells towards the sides of your head. You want dumbbells to go about midway of your head.
Make sure that you are only using your elbow joints to lower the weight and that you are not using your shoulders to move the bar back and forth.
3) Exhale and push the weight back to your starting position by only using your triceps (i.e. only moving the elbow joint).