Father of 2; reasonably confident that they are both mine; 2.5 year old girl and 5.5 month old son. My life is awesome - it's work and weekends are always a blast.
First, nothing can quite prepare you for going to the hospital with 2 people and going home with 3. Take a deep breath, you're going to get through it. In fact, take comfort that I am telling you it is totally normal to feel overwhelmed.
Before birth, go stand in line for a popular movie and go on a Saturday night to stand in line at a restaurant that doesn't take reservations. If you have the means, try to hit one last little vacation - maybe C-bus to miami and drive the Keys for 3 days. Last chance for years!
We had a high-risk first pregnancy, and that taught me a lot and humbled me. Like now: if you are fat, go to the gym and watch your diet. If you are poor, get another job or change jobs or get educated so you can change jobs. There's so much control with life, and so little control with pre-birth and even with a newborn. Embrace the control that you have, and learn to let go of things that you can't control.
Support your wife, who is going through this complicated thing you will never understand: mothering. She will worry about things that you will never emotionally understand, just know to support her. Then she will worry that she isn't worrying enough or that her worry is killing her child. Just support her. Don't argue with logical darts, just listen and empathize. Ask her how SHE is doing, and ask her if she could use anything. You are a man now, so don't run from it.
If your wife likes to read to feel prepared, my wife recommends Baby Wise, which talks about sleep scheduling and other stuff that I don't know b/c I didn't read it. As a general matter, I think babies come out as blank slates and they learn what you teach them. They can be shaped for the benefit of themselves, if that shaping benefits you. It's a marathon, not a sprint, but that's hard to recognize sometimes, particularly at 3AM.
Not all moms want to stay home with their children forever like my wife. I think that it's totally bogus that they often feel guilty about that. Just speak to your wife about what she wants her legacy to be and work together to achieve it.
In fact, speak to your wife a lot, about anything on your mind and her mind. Just keep conversations going about things, and make sure you aren't always bringing things up to debate. Just check in with her mentally/emotionally.
Learn to be hyper-respectful of all other parents, especially moms. They do things differently and in their heads, a little thing to you might be a huge deal. So when around other moms, compliment them, their babies, and how hard it must be and how you can "only imagine." When you see a pregnant lady (make sure she is indeed pregnant), tell her she looks great too, and ask if it's her first kid and get her talking, and tell her what you are going through too. As it pertains to your wife, nip anyone else's opinion, particularly mother-in-law's opinion, in the bud (especially if that opinion is not-so-thinly-veiled criticism).
Some people love/hate babies. I find the pre-smile stage particularly tough, for example. This too shall pass. You are not a bad person, you are cut out for this, etc. Just hang in there when you are really tired and grumpy - there's a light at the end of the tunnel.
Finally, as a man with 2 kids, don't stress too much - there are 6 billion people on this earth, so there's lots of ways to parent. Just enjoy it and don't forget to smell the roses.
