Generally you want to exhale as you drive the bar up, and inhale on the way back down, but when you're nearing failure you just breath any way you can!
You're supposed to breathe during a deadlift? Huh, I kinda just hold it and pull like all Hell untill I see all the pretty sparklin lights..LOL... But I basically just grab a deep breath, reach down and grip the bar, lower my body and yank for all i'm worth... Then start letting it out after lockout
I take a deep breath when it's on the ground and start to exhale when I'm through the tough part of the lift. I wouldn't think it about it too much, just do what comes natural.
HUGE air before I descend to grab the bar and exhale at top. I actually hold my breath for the first few reps of almost every set. Just a personal thing, never had any problems with it
Take as much air into the stomach as possible...reach down and grab the bar....push abs out against belt...stand up with the bar...drop the bar and exhale.
What's this rep talk?
In all seriousness, when I do happen to do reps for deadlift I treat them as a serious of consecutive singles...getting reset between each rep.