I tried lots of things...spicy food, long walks, DTD, raspberry leaf tea, swinging on a kids swing, and walking sideways up and down the stairs. I didn't try the castor oil, or EPO or nipple stimulation. Acupuncture really seemed to get things going for me. The contractions would start almost immediately after each session.
I DTD a few hours before going into labour though, maybe that was the real trick.