In broadest terms, your clubs themselves will help tell you when it’s best to use them. Each club is designed for a particular job—namely, to send the ball a particular distance at a particular trajectory. The longest clubs in your bag—the driver, fairway woods and hybrids—have longer shafts and less loft on the face, so the ball goes farther and runs out more. With irons, the shafts get progressively shorter and the loft on the face progressively increases, which means the ball will travel shorter and come down more steeply as you work your way down from a 5-iron to a sand wedge.
