Spacing your hands wider during push-ups or widening your grip during bench will force your pecs to work harder. :good
As everyone else has said, widen the hands or squeeze inwards when you do bench press. Other than that, leave the triceps out and do some flyes.
If your triceps are strong, this will make it easier to work your pecs. If they are weak, your arms would give out.......before your chest muscles where properly worked.
Thats impossible, the triceps are just a stablizing muscle. During pushing movements, like the bench press or push ups. The closer your grip is, the more stress is on your tri's.....so just widen your grip, if you want to put more emphasis on your chest muscles.
you need to pre-exhaust the pecs, using a isolation exercise followed straight away by a compound 1. for example dumbell flyes immediately followed by press. so 8-12 flyes into 8-12 press, this will be 1 set!
I've seen some guys do something like that with squats. They'll do sets of assistance exercises first and then do squats. I usually do the reverse. I'm curious, how does pre-exhausting help exactly?