Most lifters need help with their upper chests. They lack the "T" at the top of the chest that perfectly compliments a Jersey Shore V-neck shirt.
The sternal head of the pecs is responsible for humeral adduction and internal rotation. This combination is a dream for the bench press and the reason most lifters see gains in the lower portion of their chest but find dead space in the upper regions. The clavicular head is what we want to attack.
The supinated-grip chest press is one of the best ways to focus on the clavicular portion of the chest while maintaining shoulder integrity.
Bodybuilders work on the upper chests with low flyes, which is the right idea, but puts too much torque on the shoulder and not enough pressure on the chest. Going to an underhand grip and upping the weight keeps you in a safer range while blasting the clavicular fibers.
Start with 4 set of 15 reps. Begin from just below the chest with elbows directly at your side. At the end of the press, the hands should be in line with your chin at full extension. The cables are easier to maneuver and more comfortable for maintaining the underhand grip.
Mix this into the middle of your next chest workout and you'll soon see the benefits.