If you want to create a lot of clubhead speed, you need to make a good shoulder turn during your backswing. This turn, often called a "coil," lets you get the club into a good position at the top. Professional golfers, who work hard to develop extra flexibility, often get their shoulders turned as much as 100 to 105 degrees from their address position. However, the goal for most golfers should be a more modest 90-degree turn.
Place one golf club on the ground alongside your right foot -- if you are a right-handed player -- and perpendicular to your target line. This club will help you better visualize the angle of your shoulders during the backswing.
Take your address position, and hold the second club against your shoulders. This may be easier to do if you cross your arms, so your right hand holds the club against the left shoulder and vice versa. This second club will be perpendicular to the first club.
Turn your shoulders while keeping the second club firmly pressed against both shoulders. The shaft of the club will point along the angle of your shoulder turn. Remember, you are trying to turn a full 90 degrees so the club shaft should point parallel to the club on the ground. Because turning with the club held like this is easier than a regular backswing for most players, it also gives you an idea how much shoulder turn is realistic for you.
Take your address position again, but this time align the club on the ground so it is parallel to your target line and hold the second club with your normal grip.
Make your takeaway, but stop when your hands are at or just below waist high. Both of your arms should still be fairly straight – as they were at address – but also fairly relaxed. This is called a one-piece takeaway. If you have to bend your elbows to reach this position, you aren't turning your shoulders enough early in the swing.
Continue your swing up to the top of the backswing and check the position of your lead shoulder. If you swing right-handed, that's your left shoulder. That shoulder should either be under your chin, or have pushed your chin to the side to make room.
Check to see if your back is turned to the target. When you make a full 90-degree shoulder turn, your target should be directly behind your back.
Check the position of your club shaft at the top. For many players, it will be parallel to the club on the ground. This isn't a reliable gauge on its own; not all players reach this position, regardless of how much their shoulders turn. But in conjunction with the other checkpoints, it can confirm a full shoulder turn.