Congrats! 
Choosing to be a parent is the most emotional and rewarding experience of your life.
Many great comments already, so I’ll try to keep my opinions short.
The first and most important thing you can do in preparation is have everyone to get their heads out of their rear ends and accept parenting isn’t some Disneyland production of a fairytale. Sounds cold and brutal, but its reality. I was very fortunate in our family in relationship to the timeline of having kids. I’m almost 10 years younger than my next sibling and the baby boom was many years before the baby boom in my wife’s family. I was already prepared ( crapping myself) for the level of work and responsibility that was to come. My wife, and her entire family was still in fantasy mode of how “perfect” life would be. 
That was met with reality very quickly and my wife did have some difficulty adjusting.
Communication – There will never be a more important time for your spouse and you to be open and honest with each other. Your going to have days when you walk in the house needing to cut grass, change oil, pay bills….and so on and she will say “take her, I need a break”. I see so many young couples have the argument about being selfish, not doing their part, blah, blah, blah. In most cases its the lack of communication and prioritizing. As much as you’ll be told to help more, its a two way street. When my wife was in tears and needed a break, I handed her the shovel and told her to go clear the driveway and sidewalk, or go cut the grass. She needs to help you out as much as you need to help her.
Kids = ROUTINES
Want less stress and easier to manage kids, get them on a routine. Obviously a newborn will dictate your schedule for a while. But kids that have set routines are so much more enjoyable. I see whiny brats that pizz/moan to get their way, kids that won’t go to bed, don’t listen……and they all seem to have one thing in common – NO ROUTINE. When kids have a very firm structure, their personalities will reflect that. Kids learn more and fast when they are in a structured environment. If you don’t show/teach them how to be civil, respect others, and how to think responsible, you’ll have unruly brats.
Be a parent first, not a friend.
Your job is to teach that child the skill sets to be the adult they will grow into being. Spoiling them, letting things slide,…all are detrimental to being a responsible adult. It starts before they arrive preparing your mind on the best way to handle situations. Kids are a sponge and will absorb EVERYTHING you show them.
For my wife, a great set of books we were given was “What to Expect when You’re Expecting” and What to Expect the First Year”. Many questions pop up on what’s “normal”. These were great tools for my wife to look something up and calm her mind instead of calling our parents everyday.
Swallow your pride
So dang many people get sucked into wasting so dam much money on new baby crap. “Oh its so cute”, “Oh that would be nice,…” You’ll spend a fortune on crap your kid will outgrow or no longer need in months, weeks, or days. That girl will wear an outfit once and a week later it no longer fits. Buy as much necessity stuff as you can USED. Your going to spend more than you imagine on diapers and other disposables. Don’t pizz away more money. Just buy the things you find that you absolutely NEED. One exception to this – Buy packs of cloth diapers. Good quality ones! Best burp rags, cleaning rags you’ll ever own. We still have some left over that my wife uses for dusting, and other household stuff. By far, cloth diapers for cleaning rags have been the best investment of all the stuff we ever bought.
Enjoy the ride
I can’t tell you how many friends and family members think I am an absolute hard-azz on my girls. I’ve been called into question a number of times and I don’t care one dam bit. After seeing how my siblings kids were turning out and the multitude of mistakes they were making, I vowed to do things differently. I looked at the most respected individuals in our family that I strived to be like. I recognized the attributes that set them apart and was determined to teach these to my girls in daily practice. Its amazing how much pride you have when you see your kids achieve. Not the participation trophy crap, but the things that really matter.
When you see your daughter dropping “friends” because they don’t have the same morals, when they are business planning their lives and structuring their milestones, when they run across a parking lot to aid an elderly person, when they tell you in the form of a question of their most difficult decisions on what to do – your going to smile feel something unlike anything you’ve experienced and know you’ve taught them to be responsible adults.
Best wishes
