Most golf instructors will tell you to bend over from the hips when assuming your stance. It is usually taken for granted that you know how to do this.
However, in my work with recreational, semi- and professional golfers, I am continually amazed at how many do not have the ability to bend over from the hips. Most bend over from the waist and create a rounded back position in the stance. Some bend over from the hips and the waist simultaneously.
When I correct their stance, some golfers find it difficult if not impossible, to bend from the hips while maintaining the normal curvature in the spine. It often takes many repeated efforts before they understand what is invloved and what it feels like to bend over from the hips and still maintain good spine position.
One of the best exercises to learn how to bend over from the hips while maintaining the normal curvature of the lumbar spine, is the good morning. In this exercise you contract the lower back muscles to maintain the curvature of the spine and then bend over from the hips without relaxing the tension on the back muscles.
When you bend over sufficiently far, you will feel a stretch in the hamstrings. Thus, this exercise can teach proper spine position while actively stretching the hamstring muscles. In addition, it can teach you how to get into an effective stance, one that will not only protect your back, but allow for effective shoulder rotation.
For many golfers, it may take weeks or months before they become familiar with what it feels like to bend over from the hips while maintaining the normal curvature of the spine. But once learned, you will see better drives and feel a smoother swing. For more information on this and other exercises specific to the golf swing, see the book, Explosive Golf and/or the DVD, Explosive Golf.