Finish In Balance
Getting this right means everything that came before it is solid

When you watch a Tour event you'll notice two things: PGA Tour pros never make full-speed practice swings, and they always hold their practice-swing finish for a count or two. I've been doing this for years because I know if I can finish in balance to the point where I can hold my end position for a few seconds, then I've made a good swing. Finishing in the same place and in balance like this is the ultimate key to consistency and repeatability, because you can only get there one way: with a good swing. On the other hand, you can finish off balance by making a hundred different backswing and downswing errors.

The next time you play, make practice swings with the sole intent of finishing in balance, then step up and repeat that swing when you hit the ball for real, even if it means you have to swing a little slower. You'll be amazed by your results.