Along with a poor and weak grip, one of the biggest mistakes I see many of my students make is having bad posture at address. This means they're in a slumped, slouched and unathletic position from their neck down. Odds are, these students have wrongly been told to keep their head down through the swing, which means they bury their chin into their chest, and the back is rounded, and the shoulders are squeezed together. As a result, this makes swinging the club properly much more difficult, and the likely result is excessive lifting and dropping of the arms and hands. And in many cases, because the body can't make a good turn and shift away from the ball on the backswing, a reverse pivot occurs.
When I see this, I immediately make my students aware of their bad setup. Sometimes, if it's severe enough, I'll place a sleeve of balls or a golf glove on their upper back and neck. In no way do we want that to be able to sit there! I often joke with students who mimic this position that I could place a pizza on their upper back, and it would stay in place. That's no good either! We want to be more upright so the sleeve of balls can't stay in place on your upper back.
The goal in your setup (with virtually any club) is to feel tall, upright and athletic. You should feel as though you're looking at the ball with a tall, proud chin. Or, think of it this way: I like to encourage my students to "see the ball with the bottom of their eyes." This helps you keep your head in alignment with your spine.
As for your knees, they ought to be slightly flexed, and any lean forward toward the ball should be a tilt from the hips. It's always better to miss too upright with your posture than too slumped and slouched. Your weight should be over your shoelaces, not hung out on your tippy toes. And lastly, feel as though you have a grapefruit under your chin at address. This will help you avoid slouching your back and chin. Just remember, don't squeeze the grapefruit and make juice!
Try this, and I bet your drives will be longer and straighter and your irons more precise too. Top-25 Instructor Barry Goldstein is one of the country's leading golf instructors. He currently teaches at Inverrary CC in Fort Lauderdale, Fla., and can be reached via email at firstname.lastname@example.org.