Shoulder turn is tough to monitor on your own because you can't see yourself swing. To get the next-best thing, slide one of those alignment aids or sticks—I use the ones the hardware store sells as driveway guides for snow plowing—through the sleeves of your shirt so it runs along the top of your shoulders.
If you want to break par, when you're on the course you have to be a player, not a student of the swing. With the elite players we teach, we ask them to place a physical "line of commitment" on the ground behind the ball for every practice session.
The 90 scoring barrier is one that resonates for so many players: When you can consistently shoot in the 80s, you feel you're a good player. The desire to break that scoring goal can do some damaging things to your thought process, though.
Case study with Gary Woodland: Randy Smith first started working with PGA Tour player Gary Woodland back in 2005, during his junior year at Kansas. He could hit it 380 yards—but not always in the right zip code. Find out how the 2011 Transitions champion developed a more controlled, stable swing.