Bring up the rear | The missing piece in most guys' shoulder development is the rear delt, which is almost always underdeveloped relative to the front and side portions of the muscle. To bring it into balance, cut back on the amount of pressing exercises you do, and try this drop set of the reverse cable fly. Attach a rope handle to the cable and grab it with one hand. Bend at the hips until your torso is almost parallel to the floor and raise your arm out to the side until it's level with the floor. That's one rep. Perform 15 reps on both sides, and then rest 30 seconds. Perform another 10 reps, and rest 60 seconds. Finally, complete five more reps. While it's a lot of work for a small muscle group, it should be just enough to shock the long-neglected rear delts into growing.
Work the Whole Muscle | The lateral raise doesn't get difficult until your arms are nearly straight, leaving a lot of space in the range of motion in which there is little tension on the deltoids. But you can counteract that with lateral raises on an incline bench. Grab a dumbbell, set the incline to 45 degrees, and rest one side of your body against it. Perform a lateral raise as normal, stopping when your arm is slightly above parallel to the floor. You'll feel the tension on your deltoids the entire time, not just in the last few inches.
Train one at a time | The shoulders like heavy weights. The trouble is, to train heavy, you need a barbell, but then you risk the stronger side taking over for the weaker one and shortchanging it on muscle gains. Instead, use one dumbbell for your shoulder presses and hold on to something for support with your free hand. This takes the balancing act out of dumbbell work, allowing you to focus only on lifting heavy with one arm-maximizing the work of that shoulder.