The most common self-soothing method babies use is sucking the thumb. However, our kids are rather unique in the way they soothe themselves to sleep. The first two simply sucked on their mittens, then fist for Joash and fingers for Jayna.
However, the younger two are pretty interesting. Jaide will use her right hand to stroke her own left elbow. Joram will do this upper-lip sucking motion. Can't really picture that? Watch the video and see for yourself.