I have heard a lot about bouncing on the ball
You can Google it. Acupuncture and aromatherapy also have been rumored to start labor.
Sex, walking, bouncing, squats, evening primrose oil, and then there is more risky things like castor oil
I've heard lots of ways. Cinnamon stick tea, fresh pineapple, raspberry leaf tea, primrose oil, castrol oil, and spicy food.