First thing to consider is the importance of technique; avoiding injury and doing a comfortable amount of weight. Always use full range of motion when lowering the weight, and then raising the weight just before locking out your elbows (which can transfer stress from the chest onto the triceps, causing potential long term damage to your elbow joints).
Free weight movements such as barbell and dumbbells are superior for muscle growth and strength, because you must utilize multiple parts of the muscle to balance the weight. However, machines should be utilized as well - mixed and matched with free weight movements (especially if you have injuries, as machines can be safer during recovery).
In order to have a fully developed, well proportioned chest, you need to understand that there are different parts and different exercise angles that are used to hit each part. Do it right and everybody will notice.
Interior
Flyes:
3-4 sets of 10
A good place to start is the fly motion, which can be done with freeweights as seen in the diagram, or using a machine.
Upper Chest
Incline Dumbbell Press:
4 sets of 8-15 reps
The upper portion of the chest is usually the part most neglected, but very necessary for full balance and proportion. Adjust your bench or work-station to be on an incline, to isolate the upper-pectorals. Not too high where you feel it more in your shoulders, but at about a 30-45 degree angle. This will give you that wide upper body look.
Keep the pressure solely on your chest by adjusting your body placement and keeping your elbows in. Always aim to lower the weight with a controlled movement until you tap your chest and then raise the bar from that position, and NEVER bounce the bar off your chest, which will only cheat your gains and will cause injury at some point. Never use a weight that is too heavy for you to control.
Exercises such as barbell incline press, dumbbell incline, machine incline press and incline dumbbell flyes, all target the upper chest.
Middle Chest
Flat Bench Press:
4 sets 8-15 reps
The middle part of your pectoralis-major is most responsible for strength and power, which is why heavy bench press should be a staple in any athlete or bodybuilder’s routine.
Utilize a flat bench, for isolation and balanced chest development. Exercises include: barbell/dumbbell bench press, machine bench press, or dumbbell flys and the good, old-fashioned push-ups
Use full range of motion when lowering the weight and then extend to the point right before your elbows lock out. Maximize use of the chest and avoid transferring the pressure onto your triceps or elbow joints.
Bang out these workouts consistently enough to the point you get regularly confused for NHL and NFL players.
Lower Chest
Decline Bench Press:
4 sets 8-15 reps
The lower part of the chest has the shortest range of motion, as a result of your body being in a decline position to isolate that area.
Decline workouts are great, because many agree it uses the most muscle fibers in the chest and gives you the ability to focus on a nice squeeze during a workout set. They also create that appealing roundness in your overall chest development, and full symmetry in the pectoralis major.
Exercises include Decline barbell press, decline dumbbell press, machine decline press, dips, and cable crossovers.
You'll want a mind-muscle connection, so you can force as much blood into the working muscle (aka "the pump") which will lead to superb muscle growth.
