I have at times gone to a lot of trouble to find something to hold the bow in such a way that I can see where the tip of the arrow is with respect to the centerline of the bow.
Then I discovered that I could simply prop the bow against the tailgate of my truck, load an arrow, stand behind the bow with my eye positioned so that the string bisects the centerline, and instantly see where the arrow tip was with respect to centershot. Maybe everyone but me already knew about this, but for me it was one of those small discoveries that seem obvious, and made me wonder why it took me so long to figure out.