I always put my windows about half open- enough to see my sight and allow the arrow to pass as well. Make sure you wear ALL black- including on your head. I never hunt out of a blind without all black on. Also- Sit towards the rear of the blind and not right by the window. That way there are more shadows on you and your uncovered parts (i.e. eyes)
...I am not skilled to understand, what God has willed, what God has planned, I only know at His right hand, stands One who is my Savior....