* Never tell a new parent that the baby thing seems easy. It makes them crabby. (But really, they're not building rocket ships, you know? Feed, change, rock, repeat. How hard can it really be?)
* If you need forgiven for something (or want to borrow something) just offer to take care of the kid(s) for an hour or two so the parents can sleep. It's better than beer for bribing.
* Yes, singing "You Are My Sunshine" over and over can slowly drive you insane, but it's a goofy-happy kind of insane. Listening to a baby scream because you stopped singing can also drive you insane, but it's an insane that makes you want to beat your head against the wall. The first kind hurts less.
* Don't buy your friends' kids toys that make noise. Not because they'll retaliate for it someday by buying bigger and louder toys when you have kids, but because they'll put peanut butter in your work shoes now. Four times. So far.
* Change lots of diapers. Even if the mom and dad are around. It makes your friends eternally grateful and it helps combat the desire to have babies of your own (that will inevitably grow the more time you spend with them).
* Making an ass of yourself to make a baby smile will help you get laid. Seriously, even if your girl isn't a mom, there's something about a guy being sweet with a baby that will make her want to get naked with you. Maybe it's some scientific, natural mating thing. I don't know but it's so worth having applesauce smeared in your hair, sticking straws in your nose, and making elephant noises... even if someone catches the whole thing on video. And shows it to everyone at work.
* Buying cute pink baby outfits will also get you laid. Coming home smelling like baby powder will get you laid. Spit up stains on your shirt will get you laid. Having a favorite Dr. Seuss book will get you laid. If you can quote favorite lines from the book, you can probably get away with waking her up in the middle of the night for round three.