Well, IMO if you can hook your thumb behind your neck then your draw length is to long. I concentrate on the position of my shoulder blade (scapula) in relation to my spine so that I can execute proper back tension on the shot. That is my first referance point. I do not use any referances on my face because your face can tense up and change position resulting in inconsistancy. My second referance is obviously my peep sight. Once those are in position then I aim, and squeeze my rhomboids and levator scapulae muscles moving my elbow perpendicular to the string and triggering my release.