Hold the barbell (or EZ -Bar) with your hands shoulder width apart and let the bar hang at full arms length in front of you. As with several other exercises you must isolate the arms before commencing the rep and to do so, pull your shoulders down and back and make sure they stay that way throughout the exercise.
Standing as straight and tall as you can, curl the weight up towards your shoulders. Make sure your upper arms stay stationary and only from your elbows down move.
At the top squeeze the bar tight and pause for a moment and then lower at a slow speed. At the bottom completely straighten your arms.
The up movement should be fairly quick and the down movement slow and with conscious attention paid to the muscle.