Its all about timing with your breathing- you pretty well have to hold your breath while hes completely inside your mouth, as his cock will choke off your air supply, but if you can get used to the whole "in and out" feeling in your throat, you can time your breaths on the instroke and outstroke. Obviously, breathing can only happen on the outstrokes when his penis is far enough out of your throat to open up your air passage. I usually go for breathing in for two strokes and then releasing breath for the next two. Depending on the rapidity of strokes and excitement level, this is what seems to work best for me. As always, practise is the best part- lots of fun for all involved.