If you are looking to develop your pecs so that they have that cut, defined look that so many body builders and male models have, do decline bench. It works the lower part of your pectoral muscles. (they're pecs, btw, not pecks.
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By no means does that mean you can ignore the other bench workouts, like incline bench and the regular bench, but you should definitely include decline into your workout if you're looking for big pecs.