Pushups- On the way down try to pull yourself down with your back.
Bench Press- Pull the bar down to your chest.
Check out this article by Eric Cressey explaining why scapular retraction and depression are essential for the well-being of your pecs and shoulders. There is also very good information on effective and safer stretching of the pec major and minor.
*warning- The host-site of the article, along with tonnes of excellent articles, has a lot of pictures of female figure models in bikinis. It can be kind of embarrassing to look at the site, depending on the company that you keep. There is a goldmine of good info there however. For some the male bodybuilder photos may be more embarrassing. -end of warning*