There is nothing more impressive as a pair of striated, carved in stone, vascularized pectoral muscles...
By varying the angle of the incline bench on which you do your presses,
you can shift the stress from one muscle group to another. A similar
method is to change the width of your grip.
The real key in in Dumbbell
Bench Presses is lowering the weights down to as low a position beside
your torso as possible, which completely stretches the pectorals before
they are fully contracted at the top point of the movement.
By
varying the angle of the incline bench in Incline Dumbbell Flyes, you
can intentionally shift stress to specific areas of your upper-pectoral
muscles.
In Pec Deck Flyes you can vary the stress of this movement - perform it with the seat set markedly higher or lower than normal.
You can also do the exercise with only one arm at a time - movements
performed with one arm or leg at a time intensifies the stress of the
exercise, since you no longer split your mental focus between two
working limbs.