JDG,
Here is a recommendation that I use for all my students and use myself. First, hold your head still during the draw and bring the string to you, don't "go to meet it."
Then, as you reach anchor, the thumb goes under the jaw bone, the "C" formed by your thumb and forefinger cups the rear point of your jaw, the base knuckle of your index finger goes under your cheek bone and finally a finger in the corner of your mouth. That is 4 reference points.
I agree with njloco, the string on the nose only really works with the Oly style anchor (under the chin). Not too good with a side of face anchor.
Arne