My advice is to start your research & reading now. I knew this was something I wanted to do, but didn't start to seriously do some research until 22ish wks. I wish I had started sooner. Ina May Gaskin's book and "Pushed" are really good, but there are so many more. Good luck!
Re: If you are thinking of going un-medicated
Amen! I'm debating switching now, but I feel like it's so far in! I love my OB, but had I started doing my research earlier I probably would've looked into a midwife from the start.
I may have chosen a different OB/midwife. I would have asked my OB questions way earlier to determine her practices/beliefs when it comes to things like pitocin, C-sections, early induction, etc. These are things I didn't think too seriously about prior to my research. Obviously, there's a chance I may still need some of these things, and you can never really predict what's going to happen come the day, but I would have asked more/better/different questions of my OB from the start.
I'm going to add: the book Your Best Birth is good, as well as anything in the Sears Parenting Library, and Birthing From Within.
And don't take the hospital birth classes. Although I'm sure some hospitals do a good job of explaining non-medical ways to relieve pain, most do a poor job of it. Take a Bradley class, or read Natural Childbirth the Bradley Way, or take a Hypnobirthing class (or get the books/cds). This is my Bradley instructor's resources site, lots of good websites and books.
But most importantly, be informed. Even if you don't want to go all natural, at least know what an epidural does exactly and what some side effects may be. Know what inductions are like and when they are necessary and when they aren't.
I could go on and on....I'm working on getting more of my thoughts in my personal blog.