My wife and I set up sleep shifts during the first two months. I would sleep from 9 PM to 3 AM, then we'd spend an hour all together, then she'd sleep from 4 AM to 10 AM. During a person's sleep time, they were not to be disturbed except for an emergency. We'd also sleep anytime the baby was napping.
It kept us sane. Just knowing that we would each get hours of uninterrupted sleep was great.
+1 to this method. Prior to having a reserved ~6 hour slot of sleep the lack of sleep was getting BAD.