People can tell you about the sleep deprivation and stress.....but you don't understand. Closest analogy I could come up with for the first 12 weeks was like being a Russian defender at the battle of Stalingrad.
Lots of good advice here. My two cents: get a good baby bag for travelling(visiting friends/doctors). Keep 2 changes of clothes and at least half a dozen diapers in it always. A good ointment is a must (desitin, Bodreus Butt Paste, Triple Cream, etc.) .Use regularly to prevent diaper rash! If early on the baby becomes attached to a particular toy.....buy a backup! One is none, two is one!
Lotta good advice about keeping the wife rested and happy. Believe me....she will make you believe in demonic possession (mine started yelling at me about the way I tie my shoes. Seriously.) The more you can do in those stressful first weeks, the more rested and reasonable she'll be.
I can honestly say, though, that it is all worth it. You think you know love, and then you hold your child in your arms. For me, the impact was immediate. The moment I held my son the night he was born, my life changed. It was about him (and later his sister) from that moment on.
Last thing for now.....Lansinoh brand baby wipes. Softest, gentlest wipes out there. My little guy talked early, and if he had a bit of a rash and I reached for the Kirkland wipes, he'd say" No hot wipes, daddy!" Guess they kinda chafed his little bum....the Lansinoh were good even on a rash, though.