Breathing
People make a big deal about the "proper" way to breathe while bodybuilding, its really not that complicated: Don't hold your breath! Many people claim that the "proper" way to breath is to breathe in sync with the reps and to exhale while pushing, I say that is BAD. If you breathe in sync with your reps it encourages you to do fast reps with bad form because you are out of breath and want to get some more air ASAP! Think about it, why would you want to deprive yourself of oxygen when you are trying to give 110% effort during your set? What I personally do is take 3-6 breaths for a complete rep, that way I can do nice slow, controlled, reps without turning blue in the face by the last rep. When I breathe during sets, I don't try to synchronize them with anything but I do make an effort to make sure that I constantly am either breathing in or out - never holding my breath.
Some people like to breathe really fast and shallow like a steam engine locomotive going up a steep mountain, if you do this you need to be very careful that you don't hyperventilate. Steam engine breathing does insure that you will never be holding your breath which is a good thing.
When you are trying to crank out that last rep its tempting to hold your breath to 'pop' that last rep but don't do it. When you hold your breath, your blood pressure goes up, your face turns red, and your veins start popping out and you could cause all kinds of health problems. While it looks really cool to be vascular and even have veins popping on your forehead, raising your blood pressure like that just doesn't do your body a whole lot of good. Please remember, Don't hold your breath!