Chances are that you've heard of "the slot." It's a position halfway into your downswing from where you can hit the ball on a slightly in-to-out path. You might think of it as the lower part of your swing plane, starting at the point when (if you're a right-handed player) that your right elbow drops down close to your right side.
Address the ball normally. Everyone's setup is slightly different, but your feet should be about shoulder-width apart when using your driver and slightly narrower for the shorter clubs. Bend forward from your hips so your spine leans toward the ball and your knees are slightly flexed as if you were squatting to lift something. Let your arms hang down, with your triceps resting lightly against your chest and the club head behind the ball.
Start your takeaway by turning your shoulders, keeping your arms relaxed without bending your elbows. With your triceps resting lightly against your chest and your knees slightly flexed, you'll be able to turn your shoulders and carry your hands (and the club) to nearly waist high before your right elbow will need to bend. You'll have made most of your shoulder turn at this point.
Bend your right elbow toward your right shoulder. This will simultaneously cock your wrists and allow you to finish your shoulder turn. When you finish this part of your swing, your shoulders will have turned roughly 90 degrees from your address position, pointing the club shaft down the target line and parallel to the ground. A quick checkpoint: At the top of your backswing, your right shoulder will be visible underneath the upside-down V formed by your hands and forearms, and your right forearm will be parallel to your spine. Your hips will be turned slightly to the right and your left knee pointing slightly behind the ball. You'll feel tension in your right knee as it resists your hip twist; this is what most golfers refer to as a "weight shift."
Drop into the slot by letting your knees return to their address position – both flexed – and let your arms drop slightly so your right elbow moves closer to your right side. Although this action causes a chain reaction. Your hips will start to unwind, your shoulders will start to uncoil, and your downswing will start. Dropping into the slot feels as if you are just exhaling so you can relax for an instant – but only an instant.
Hit the ball as hard as you want. The "relaxing" started your hips unwinding and, as Ben Hogan wrote, "After you have initiated the downswing with the hips, you want to think of only one thing: hitting the ball." Once you're in the slot, it's hard to go wrong. All you need to do is straighten your right elbow, finish your downswing, and hammer the ball toward the target.