I used to be stuck.
By that I mean my downswing came so far from the inside that my body would get in the way of my approach to the ball. I'd hit a lot of pushes and hooks off the tee. One thought I now use to control my path is to feel as if I'm hitting down on the outside part of the ball. That gets my downswing more on line and produces straighter shots.
You might be thinking: No thanks, I already cut across the ball from out to in. Well, if that's true, then my key isn't for you. It's meant for players who are hitting shots that either fly on a straight line but right of the target or over-curve to the left. If you struggle instead with a pull or a slice, you need to do the opposite: Feel your right shoulder lower than your left shoulder as you swing down to impact. And you want to imagine you're hitting the inside part of the ball.
Scott Piercy tied for fifth at the 2013 PGA Championship and has two wins on the PGA Tour.