One of the effective bicep exercises is concentration curls, which is performed with the help of dumbbells. Choose a dumbbell of an apt weight that you can comfortably lift and work with. To do concentration curls, you need to rest arm on thigh, lift it up and bring it down steadily. Keep your head down, and closely follow movement of arms. Continue the motion for the least of 20 times. After an interval of 2-3 minutes, exercise another set of the exercise. Doing it correctly will ensure strengthening, toning and building of arm muscles, which includes biceps, triceps and forearm.