I took prenatal classes but the most effective thing for me when I was in labour (two times, both natural and drug-free) were the breathing exercises and "low tones". Maybe google that and see what you find. Doesn't take much practice, just someone to remind you to do it if you forget in the moment!

Prenatal yoga. I did it religiously twice a week and I really think it helped.

Lots of sitting on a birthing ball (exercise ball) to help the baby drop (or so they say). Lots and lots of walking to get your body in shape generally.