On page 37 of Be Prepared, Gary Greenberg & Jeannie Hayden's excellent guidebook for new dads, are four policy suggestions for dads dealing with PPMS (Post-Partum Mood Swings. If you don't know yet, don't worry.). The other three--listen, ignore occasional belligerence, get her out of the house regularly--are good to do, too, but for us, one policy in particular proved absolutely crucial for getting through the first couple of months:
Everything But Breastfeeding
During those early weeks of two-hour feeding/sleep/diaper cycles, we basically split the work right down the middle: breastfeeding/everything else. Try it at home!