The pectoral muscles are particularly complex. Training them is a major bodybuilding puzzle only the world's greatest detective could solve. Isolating the chest is difficult because the shoulders and triceps often take over on big pressing movements. The triceps typically fatigue earlier than the pecs, making it hard to hit the chest to actual failure.
Here is a good chest workout at the gym for mass that I've used to build a bigger chest. Make sure you are getting proper nutrition so your body has the materials it needs to build you a bigger chest!
Flat Dumbbell Bench Press
incline dumbbell press
Barbell Incline Bench Press
Flat Bench Dumbbell Flyes
Dumbbell Decline Bench Press
