There's always lots of arm flapping and foot stomping on this question, mostly because each of us is built different and might find a different fit than "standard" works best for us, the gun style, where we hunt, and what we wear.
My rule of thumb for me tries to take all that in. Put on your usual clothes for hunting or shooting, hold the gun at your waist and get real relaxed and comfortable, then close your eyes and shoulder the gun. Now open your eyes and see how the sights line up without moving your head. If the gun is a real good fit, the sights are going to be lined up just about perfect. If you have to move your head around to find them, then you need to either change the way you hold the gun or change the gun.
I do about the same thing when shooting on the range, but include the target in the process. If when I open my eyes the sights are lined up right but not on the target, I shift my feet to bring the gun on target rather than torquing my body around. If you do that, it takes a whole bunch of the tension out of your body, and fully relaxed results in nearly perfect shooting position. Only very small adjustments to the aim are needed. I just shoot a whole lot better offhand if my body is fully relaxed rather than all torqued up and tense.