I've been wanting to work on my chest...especially since my pectoral muscles are different sizes...are there any specific weight lifting that can help them seem even...i know this problem happens with biceps and lifting and such, but pectorals? thanks for any suggestions

Dumbell benching.

one arm or both?

Both, but one arm is good as well if you use the same weight with both arms since it hits your core hard.

MOS - agreed. Also; when you're doing pec dec for example - lower the weight and do one arm at a time. If you have a dip machine, lower the weight do one arm at at time.

If you want your chest to reshape itself then pay close attention to any exercises you do that include the pec as either the hard target or soft target muscle and find a way to do them one side at a time.

And if you want to even them out, don't do extra reps for the smaller one, but just add volume.

it could be genetic, so it might be harder to fix than normal but if you try whats listed above it should hopefully balance.