Going through Ben Hogan's book and rebuilding my whole swing according to his five fundamentals.
1) Switching from interlocking to overlapping grip.
2) Moving my right thumb across the handle so the v-notch points up at my chest. I used to always have that classic strong thumb down the middle of the grip, which I think is part of my slice problem.
3) Trying to keep elbows in tighter together at address.
4) Slight angle forward with my left foot (I'd always had both feet perpendicular to my target line).
5) Trying to concentrate on my right elbow not flying out...keeping it tucked into the body.
Amazingly, these are all things I've pretty much ignored (not been aware of) for the first 20 years of golfing!