Lots of good advice already!
Before you go to the birth center (assuming your labor isn't going really fast) spend some time cuddling, kissing, fooling around with your partner. That helps to get things going.
Buy a new, large cartoon book and keep it wrapped up until you are in labor. Cartoons are great to read while you are hanging around, stretching and such, because they work with a short attention span and help you keep your sense of humor!
Keep upright as much as possible and do lots of walking around, to help the baby move down.
Perineal massage in the weeks BEFORE labor started felt really good, and I wish we'd done more of it. (I could not reach the area well enough to apply pressure, so my partner was doing it, but he kept not getting around to it.) My midwife tried to massage me between contractions, but it was insanely painful then and I could not tolerate it! Being more flexible there might have helped me avoid the episiotomy.
Make a little "file" in your mind of images, songs, and quotes that seem like they might be helpful to you during labor. Go over them in your idle moments. Then they'll be likely to pop up just when you need them. For example, in my last trimester I saw an episode of "The Simpsons" in which Flanders tries to vanquish a sinful thought by drastically yanking his mustache and shouting, "Pain is the cleanser!!!" I "filed" that and managed to think of it when the baby's head was crowning.
Bring mouthwash, in a flavor you really like, in case you throw up during transition. You will want to get the taste out of your mouth to take the queasy feeling away, but you probably won't have the time or coordination to go brush your teeth.
If you feel a strong urge to do any particular thing, there is probably a good reason. Do it, even if it seems silly or irrelevant.
SPEAK UP if anything anyone's doing feels wrong to you. My partner and I are still kicking ourselves for the things we did not speak up about. In every case where we DID speak up, we feel it improved the situation.
I hope you have a fabulous birth!!