We’ve all seen Jack Nicklaus tilt his head just before starting his backswing. He’d cock it to the side a little, looking at the ball out of his left eye a little more so than out of his right.
It’s a relatively simple trick that can have a massive impact on your game. Looking at the ball out of your left eye (for right-handed golfers) forces the shoulders closed a little. Looking at the ball out of your right eye forces the shoulders open a little. Thus: look out of your left eye for a more inside-to-outside swing (draw or hook) and out of your right eye for an outside-to-in swing path (fade or slice).
I’ve personally used this drill to affect the shapes of my shots. The changes it makes to your swing are natural and need not be thought about while “the machine is in motion,” yielding consistent results. Give it a try and see if it works for you.