Expect labor to take longer (i.e. don't get scared that "something's wrong"...posterior babies come out, it just takes longer...remember, you are safe and your baby will come out! That was the hardest thing for me with my dd1's birth. She was posterior with an asynclitic head and labor took 40 hours even though she eventually turned anterior. I was so scared that something was wrong since I had NO idea labor could last so long! Being scared made it much harder to relax and give her the room she needed to turn back around).
Have someone(s) there to put counterpressure on your back--it helps a lot.
You won't necessarily feel "painless" between contractions (although I must say, with my second who was anterior, it still didn't feel painless between contractions!)
Try to get your baby in a better position now if you can...there's still time, and it certainly is a bit easier to birth an anterior baby than a posterior one! Check out www.spinningbabies.com--they
have great reccommendations like:
Don't sit "back" in cushy sofas, easy chairs, recliners, etc.
Do sit forward with your back tilted forward and your knees lower than your belly (I got one of those funky chairs that has you basically kneeling on a pad below the seat...it puts you in the "right" position)
Try to sleep on your side with your leg up on a pillow so that you're slightly tipped over your belly (NOT on your back)
Crawl around on all fours as much as you can during the day
"Hang" your belly for 5 minutes a day to encourage your baby's heavy back to fall towards the belly side instead of the back side (lean forward with your head/upper body on a cusion on a table and your feet on the floor so that your body is in a 90 degree angle--relax as much as you can for 5 minutes and let your belly hang)
Good luck! You can do it!