Lots of women ask what they can do to get labour going when their expected date of delivery goes past. Some women try sex, hot curry, sex and a hot curry :-), a long walk, nipple stimulation. We do not recommend the taking of castor oil to try and get your labour started, it can cause nasty stomach cramps, diarrhoea and you still end up not going into labour.
This interesting article discusses the folklore.
"“There are all kinds of obstetrical folklore and old-wives tales out there,” says Jonathan Schaffir, associate professor of obstetrics and gynecology at Ohio State University and lead author of the study, published in the June issue of the journal Birth. “If it’s not something perceived as being harmful, patients think there’s no downside. Even if it doesn’t work, it’s something to pass the time.”