When it comes to the barbell curl a lot of guys let their ego take over and pile lots of weight on the bar and start curling away while allowing there back to swing half the weight up. When they do this they don't realize that the bicep actually isn't under to great of stress. When doing a barbell curl plant your heels to the ground firmly to brace your body and prevent you from swinging your back. When performing each rep be sure not to let your elbows go past your hips because that will take tension off the biceps. Think all the action into the bicep and thats where your power will go. Curl the barbell up as close as you can to your chin and at the very top of the movement squeeze your biceps as hard as you can. Hold the contraction for at least 1-2 seconds, and lower the bar all the way down to the starting position with a slow controlled 2-3 second negative. The negative portion of the rep helps to expand the muscle tissue and to build strength. Doing slow negatives has greatly increased the size and strength of my biceps. A lot of guys will curl the weight to the top and just drop the bar down to starting position. Dont do that! follow all these guidelines to performing a barbell curl and your biceps will start growing. Also dont be that guy who does 50 sets for biceps. If you want them to grow you do need to train with high volume and target them from different angles, but typically 12-16 total sets is plenty to pump the biceps full of blood and destroy each and every muscle fiber. Divide those 12-16 sets between 3-4 different exercises to ensure you're targeting different areas of the biceps. To fully build them you need an exercise to target the inner head, the outer head, the peak, and the brachialis. You can target the inner head with a wide grip barbell curl. You can target the outer head with a close grip barbell curl. You can target the peak well with concetration dumbbell curls or preacher curls. Either or will do fine. You can target the brachialis with a reverse barbell curl or hammer curls with the dumbbells or rope cable atatchment. Now get to the gym and put this info to good use and watch your biceps grow!