Bench press for the chest is a little trickey. You can not just lay down on a bench do a couple of reps and think that your chest is just going to blow up. That works for Arnold but not the average gym rat. We need to look at doing the bench press a little different.

Getting a thicker chest from the bench press requires to look at the exercise and all the different things going on with it. The chest, triceps, shoulder, lats, traps, and even the biceps are involved with the bench press. But to get the most out of it for the chest when need to try to minimize the other muscle groups while trying to maximize the chest involvment.

First will be the set up. Before you lay on the bench just sit on the end of it and picture in your head the top of the rep in a seated row. Chest is out and the shoulders are back and down. That is how we want to lay on the bench, chest arched, not the back, and the shoulders are pulled back and down. Keeping the shoulders back and down reach up and grip the bar a little wider than shoulder width and unrack it. With the bar held directly over the chest start lowring it down towards the collarbone. While you lower the bar your elbows should be direct under the wrist so that when the bar bottoms out the arm makes a 90 degree angle. You should feel the outer side of the chest muscles pulling as the bar goes down to lightly touch or graze the collarbone. Once it touches the collarbone start pushing back up, there is no pause at the top or the bottom of the rep, the weight keeps moving at a slowed and controlled pace, never pausing between reps, keep moving within the set. Some people find it easier to use a machine to perform the bench press this way. You have to find what works best for you. But when the bench press is done this way just about all the stress is on the chest.

I tell people all the time, to think about what the function of the chest muscle is. The chest muscles or pecs are to pull the arm up and across the chest. If you will keep that in your mind when doing the bench press you will lift a little different. You will focus on pulling the weight up and across instead of pushing the weight up. Squeeze the weight up do not push the weight up. Muscle it up, do not power it up. Focus on the chest and what it is suppose to be doing and not just forcing the weight up. Working out will also require you to think and focus, do not just go through the motions.

references:
weight bench
Best Weight Bench