Early I published an article that explored the journey that your hand makes going behind your back and eventually holding your big toe in Ardha Baddha Padma Pashimottasana.
Now there is a video where you watch the journey and learn about the detours and road blocks that you could run into along the way.
If you would like to watch it directly on Youtube you can use this link. http://www.youtube.com/watch?v=jAKKSw9qH74