Sex!!! Worked like a charm with my first child. Had sex about 11ish then work up with pains at about 1am then went hospital and got there at 5.30am and my daughter was born at 9.33am. There's loads of other things you could try but I would say at least give it a try if you can. There is actually a hormone in your man's semen that softens the cervix and if you were to have an orgasam then that encourages contractions as your uterus kinda contracts anyway when you orgasam.
Try drinking pineapple juice