Fadi
...
It's all about control. Breathing is one of the most fundamental bodily functions and yet most people cruise through life, and even through workouts without paying their breath any mind at all.
If you can be aware of and acutely in control of this most basic of bodily functions throughout you daily life and especially when exercising you may find that you have much more control of the more complex functions you perform during your exercise such as deadlift/benchpress ect...
As for when to breathe in/out, Id recommend breathing in when you are relaxed and breathing out when you exerting yourself as a general rule...
I also recommend abdominal breathing in between exercises to restore energy and even out the heart rate.
Just out of curiosity Tekkerz: Military press and squats; How would you breath in these two lifts? Thanks.
Fadi.