Do not use castor oil. Some people have and it didn't do anything. But it can cause you to have diarrhea and it can cause your baby to poop in the womb which is more dangerous. If that's your last option, you'd be better off waiting for your baby to come on their own time.
It's basically concoction of stuff you drink.. my sister in laws doctor told her to drink it when she was ready and after she drank it she was in labor few hours later
2 tablespoons of almond butter
2 tablespoons of castor oil
250 ml of lemon verbana tea
300 ml of apricot juice
Blend all ingredients until smooth (drink with ice cubes and it goes down easier)
4 kids later and none of the things I've ever tried had ever worked. As a doula I can tell you that the likelihood of doing anything that will actually start labor is very slim. The methods said to kick start labor are generally better for getting labor going once it has already started.