Here are some tips for effectively training the biceps.
1) Use a supinated grip. Supinated means to have the palms face up during the exercise. This hand position will put the greatest amount of stress on the biceps muscles.
2) Make sure your wrists stay straight and neutral. Especially when using free weights, the wrists can have a tendency to hyperextend causing potential injury to the wrist joint. Keep them straight!
3) Incorporate free weights into your arm routine. Free weights are always more effective in that they recruit more muscle fibers and call synergistic muscles into action as well. The core is also called into action for balance and support.
4) When using barbells, grab the bar at a width that is slightly outside of the shoulders. The best way to assess this is to stand in anatomical position with the palms facing away from the body. Wherever your hands fall is where you should grasp the bar. A closer grip can cause potential injury because the shoulders become internally rotated.
5) Make sure to keep the feet planted at about shoulders distance apart, with the knees soft (not locked) and the belly button pulled inward toward the spine. This is called the "supported" position and will help to prevent the lower back from arching.
6) When curling the arm, try to avoid any movement at the shoulder joint. This will involve the shoulders in the exercise and take away from the work that is being done by the biceps. The elbows should remain at your side and not shift forward or backward. If done correctly, the bar should not touch the chin at the top of the curl, an action that has been rumored to be correct. However, this belief is a misconception. Also, make sure that you do not fully extend the arm at the bottom of the movement. When this happens, the biceps relax. In order to achieve the full benefit of the exercise, you want the biceps to be in tension for the entire duration of the set.
7) When using machines, it is important to line up your elbow with the machine's axis of rotation. This axis is almost always depicted on the machine and is easy to find.
8) Do not vary your grip on the barbell. Some people believe that by having a narrow grip on a barbell, you can isolate the different heads of the biceps. This is not true. As I said before, make sure you grab the barbell with a grip that lies slightly outside the shoulders.
9) Incorporate variety. As with everything else, variety is the key to finding results with arm training. Keep trying different exercises. And for advanced lifters, make sure you are increasing the intensity and lifting heavy on a regular basis.
10) Don't expect any certain "look". The shape of a muscle is genetically predetermined. So don't be expecting your biceps to look exactly like they do on that hot guy in the gym. Yes, they will grow and change in appearance, but the shape will remain the same.