Going into labor is something that your body does naturally, but sometimes people want to know how to go into labor because the baby is overdue and they're concerned, or perhaps just tired of being pregnant! While there is no way to guarantee that you'll go into labor, there are things to do which according to some people, may help the process along.
If you're trying to go into labor, go for a walk. I did this with both of my (overdue) kids, and it worked both times. Unfortunately, going for a longish walk may make you tired before you begin labor. I did this in the evening. If I were going to try it again, I'd do it in the morning, so I wouldn't be so tired when labor started!
Eat some spicy food, especially food containing cumin. The reason this may sometimes work is because stimulating the intestinal track may cause you to go into labor close to the time when it is ready to start anyway.
Invite a friend you haven't seen for a long time to come and visit you or attend the birth. If you think you'll have a couple of days to "catch up on old times" you will go into labor so that you're so exhausted that you barely register the fact your friend is there. This technique also "worked" for me twice.
Sex. Sex can make you go into labor if it is getting close to starting anyway. Semen has hormones (prostaglandins) that can start labor. And it's fun. And you will not be doing it for a long time once labor does start!