here is an example.
http://www.youtube.com/watch?v=Nb3qmsNbTqE
I actually have a special foot to do SID. I compare it to a plough in the field following a row. The little guide follows the seam line.
It really helps to have all the seams pressed to one side when doing SID or the needle wants to jump to the low side. I call that MAD or meandering around the ditch.