The pec major (above, left) attaches (originates) on the clavicle/collar bone and the sternum. It inserts on the inner side of the upper portion of the humerus.
The pec minor (above, right) attaches on ribs 2-5 and inserts at the scapula.
Flexes the arm at the shoulder
Medially rotates the arm at the shoulder
Adducts the arm at the shoulder
- Stabilizes the scapula, pulling it forwards and downwards
One of the best exercises to target the pectorals, and overall upper body strength, is the bench press. Unfortunately, many hit the bench press with little idea of how to target the chest more effectively.
I highly recommend checking out my How to: Bench Press guide to teach you the subtleties in order to help you properly focus on targeting the pectorals and take some of the stress and strain off of the anterior deltoids.
Barbells or Dumbbells?
There are pros and cons to training with both dumbbells and barbells, especially when it comes to chest training. Barbells generally allow you to press more weight, therefore stimulating more muscle fibers. Having said that, your hands can be "stuck" on more of a fixed track. Dumbbells force a bit more stabilization from your chest and shoulders, and can potentially even activate more from your triceps. Ultimately, the best training program effectively uses a wide range of training styles such as barbell training, dumbbell training, as well as other closed-chain exercises like push-ups.
One nice thing about training with dumbbells is that you can get medial rotation out of your humerus. In other words, if you were to do a close-grip dumbbell press, palms are facing one another when the dumbbells are at the sides of your torso, and as you press the dumbbells up over your chest, pronate your hands so that the heads of dumbbells meet over your chest, and your palms are now both facing away from your face.
Whenever you are working your chest, your shoulders will be involved. I highly recommend my in-depth and thorough warmup to get the upper body prepared for the workload and demand.
(Some of) My Favourite Pectoral Exercises
You can find more of my favourite chest exercises in "Triple Threat" - Free 30 minute Chest, Shoulders, & Triceps Workout as well as in my April 2015 edition of TRF+ - 30 minute Chest & Back.