Natural Induction

I was wondering what natural methods could be used to bring labour on a little sooner and when can I safely start trying these?

I ask because my doc would like to induce at around 40 weeks (I do have to really as DH goes away 2 weeks later) because he says baby is getting big, I am not really worried about that as it is very possible to do natural with a 3,6kg baby. And I would like to try somethings to keep things as drug free as possible.