The most convincing method I've read about is a mother who did nipple stim for 7+ hours! I researched this quite a bit because with my first I didn't go into labor before 43 weeks, then agreed to an induction. If we do it again I will still wait until 43 weeks but will try the extended nipple stim. For this woman she would get contractions withthe stim, which would trickle off when she stopped. So she kept it up until she hit progressive labor, which took about 7 hours. Then she was 5cm and it kept up without the stim.
Myself I tried castor oil, acupuncture, spicy food, jogging, acupressure. I would try the acupressure again but get someone else to do it, and do a long session.