Bicep Curls
Variations: Barbell, Dumbbell, Preacher curl, Bicep Curl Machine, Incline curl, Cable/Resistance Band Bicep Curls
Hold weights in hands, palms facing out, elbow slightly bent. Keeping abs tight, bend the elbows and bring the weights towards the shoulders (don't touch the shoulders), keeping elbows from moving back and forth. Slowly lower back down, but don't straighten the arm entirely--keep tension on the muscle throughout the movement. If you find you're swinging the weights to get them up, lower the weight and slow down.
Keep your elbows next to your torso but don't prop them on your waist to help you lift the weights. That's called cheating.
Concentration Curls
Kneel on floor or sit on a bench and grasp a dumbbell. Place the back of the upper arm on the inner thigh and lean into the leg to raise the elbow a bit. Raise dumbbell to front of shoulder and then lower until arm is almost fully extended.
This variation puts your arm at a difficult angle, so you may find you'll need less weight than in a traditional curl.
Hammer Curls
Hold chosen resistance, palms facing each other, elbows slightly bent. Keeping abs tight to steady the torso, bend the elbows and bring the weights towards the shoulders (don't touch the shoulders), taking care to keep the elbows from moving back and forth. Slowly lower back down, but don't straighten the arm entirely--keep tension on the muscle throughout the movement.
Changing your hand position adds difficulty as you target both the biceps and the forearms.
Vary Your Workouts
Change your strength training routine by varying the exercises:
After 4-6 weeks, change at least one component by choosing a different type of resistance, exercise, position and/or movement.
http://exercise.about.com/cs/weightlifting/l/blsamplebicep.htm