Just keep in mind that this trick is quite unpleasant. Nausea, vomiting, and diarrhea are likely to occur. You also run the risk of becoming dehydrated, so consult your doctor about the risks and consider the side effects before deciding to give it a try.
For the best chance at results, some sources say you need to rub the whole areola, not just the nipple, three times a day for around an hour at a time. If you've got three hours a day to devote solely to nipple stimulation, it's worth giving it a try!
If your baby hasn't dropped yet, walking might also help him move into a better position for birth, which could help labor start naturally. Just make sure not to wear yourself out — labor is exhausting enough without having walked a marathon beforehand.
Each pineapple contains only a small amount of bromelain, so you'd have to eat large quantities (we're talking several pineapples) for this to possibly work. Eating several pineapples will likely have the same effect as a spoonful of castor oil, so if you end up eating six or seven, be prepared for the probability of an upset stomach.
Acupuncture is another method that focuses on specific points on the body, by inserting fine needles. Just be sure to talk to your doctor before trying this treatment.
Talk to your doctor before trying this method. Women with certain pregnancy conditions, like placenta previa, shouldn't use it.