Watch this hook
Every element of your setup has a consequence for your swing. For example, ball position affects the moment when impact occurs, as does stance width, hip action and, today's topic, foot flare.

The same amount of foot flare won't have the same effect on every golfer's swing, due to physical characteristics and different combinations of swing mechanics, but there are some basic guidelines that you can use to find your ideal foot flare.

                    

To increase your ability to turn back and through the ball, flare your feet between 15 and 30 degrees at address, depending on your flexibility. The less flexible you are, the more a flared back foot will allow you to turn behind the ball and then approach the target line from the inside on the downswing.

The correct amount of flare in your front foot at address makes it easier to rotate your front hip and knee correctly as you swing through the hitting zone. If your swing is too steep, use more flare; if it's too flat, use less.

Foot flare can also change the timing of impact. You can either delay impact or make it occur sooner, depending on whether you're hooking or slicing. Turning your front foot out delays the straightening of the front leg; therefore you'll contact the ball a fraction of a second later and this will decrease your hook. Squaring your front foot hastens the straightening of the left leg so that impact occurs sooner, which is good for your slice.