A couple tricks that might help you for chest if you arent already them are this. Remember its more about how you perform the exercises rather that what exercises your doing.......
1) With pressing movements, push with your elbows NOT your hands. Forget about your forearm and hand, the focus is from the elbow down as the main goal is to bring the two humerus bones as close together as we can get them. Your elbow acts a a hinge joint it should NOT be travelling up or down very far. And keep you shoulders pinched back and pushed down at all times. If they come out of this position to get the weight up the weight is too heavy.
2) With any barbell movement when you are pressing, in your mind, try to bring your hands together and bend the bar. The heavier you go the harder this will be to do but doing this ensure the pecs are engauged at all times.
3) Last but not least, and you see EVERYBODY doing this. Flys.....from your elbow to your hand should NOT be moving and arms should not be bent very much. If they are going to move then make sure it happens near the top of the movement and UNBEND then to get the two humerus bones closer together by allowing the DB not to touch too soon at the top, if you can even get them to touch, if youre doing the exercise correctly they wont. And again shoulders BACK and DOWN .
Hope some of this helps!