A few things that I've learned in the last 18 months:

1. In all things "baby", embrace the parenting path of least resistance.
2. It's a fallacy that you need uninterrupted sleep to function. Existing as someones' all-night smorgasboob o' snacks and comfort, while not necessarily a personal ideal, is actually much easier than it would seem at first.
3. Although some nights of co-sleeping (or not sleeping rather) suck massively, you can be fairly sure that for the most part it's still the easiest way for everyone to get (most of) the sleep (and food) they need.
4. There are only a few big-ticket items worth buying before you have a baby. These include a king-sized bed and a DSLR camera.
5. No one has invented a cloth diaper insert that can withstand the full force of my child's overnight bladder (see previous comment regarding all-night eating). While noble, 24-7 cloth diapering is not the parenting hill worth dying on. Slap a disposable on that butt and let 'er ride for the next 12 hours.
6. Whatever substance is in disposable diapers defies all laws of physics with it's absorbency. It's like a blackhole of wet. The only logical explanation is that someone got a patent based on a pact with the Devil. It was worth it.
7. Although you "can" start to feed solids to a baby at 6 months, some kids (mine) are not really interested in food until much, much, much later (maybe someday soon in fact). They will continue survive and even thrive on the occasional scrambled egg and massive quantities of frozen blueberries. In addition to the all-night nursing. Clearly.
8. Enjoy the period of time between when they learn to sit up and discover self-locomotion. These are the golden days of infancy. After that you will never have another quiet moment while they are awake until they move out of the house. At least it feels that way.
9. Kids will always move onto the next stage before you are prepared for them to. Parenting is a game of perpetual catch-up.
10. Babies, like fine wine, improve with age.
11. The person you created can become one of your favourite people on the planet before they even learn how to talk.
12. Being a parent will show you that you have far more patience than you ever thought possible for the people that matter to you. And far less for the people that don't.
13. Deciding to skip the prenatal classes and advice books was a good call. The war-stories of friends are far more valuable I feel.