I've been working on my form for about a year now.  I have no problems getting my string arm in alignment with the arrow as well as my shoulder alignment parrallel with the arrow.  

One thing I did notice while checking my draw length (because it has increased with these alignment issues I've been working on) was that I sometimes let my head "float" forward.  It happens when I'm fatigued, which says that I'm moving my head to make sure I get to my anchor.  

What do I do to ensure my head stays in the same position everytime?  I once read a suggestion to rest my chin on my bow arm shoulder, but that is uncomfortable.  I'm talking pre-fatigue here.  I got to learn to just hang it up for the day when I'm too tired to continue.  Thanks...Mike

This may seem like an odd suggestion, but for me, wearing a Fred Bear style hat helps.  I set the brim so that if I'm holding my head where it should be, the brim doesn't interfere with my shooting.  If my head starts to nod forward, the brim will hit the string when I draw the bow.