A correct posture is important to allow the body and arms to move freely back and through toward the target. Begin by standing upright with your shoulders pulled back and your feet about shoulder width apart (slightly closer for short clubs and slightly wider for woods). Tilt forward at the hips until your arms hang freely down and the clubhead can be lowered to the ground (preventing the shoulders from slouching forward). Taller people may need more tilt than shorter people may. Now let the air out of your knees (slight flex) to allow for an athletic position prepared for motion. You will find your buttocks will need to counter balance your upper body. This may feel stranger than it looks, but one check in a mirror will show you how normal and necessary it is.
Balance plays an important role in ball contact, consistency, and power. Without good balance at address, you cannot have a repeatable swing. You should feel your weight evenly distributed on your feet (from the heels to the balls) so that during the swing you can move your weight without having to change your posture. Some people will feel this in different places under the foot, but the key is being truly balanced.
The rear shoulder will be lower than the forward shoulder and the spine slightly tilted backward. This is due to one hand being lower on the club than the other while keeping our shoulders parallel to the target line.
The posture at address is to be maintained throughout the backswing. At the top of your backswing, you should see the same flex in the right knee and the same tilt in the spine. This is what we call turning into your posture. There may be some lateral movement, but the spine angle should be maintained through impact. Any change in the spine will alter the swing plane, angle of attack, and path.
The last thing in the stance that is often overlooked is the ball position: how far from the ball you should be and where, compared to your feet, the ball should be played. This varies with the club, player, and body type. A general rule of thumb is the ball should be played further forward for a longer club than for a shorter club. A flatter swing needs a ball position further from the body and an upright swing a closer position. A poor lie would warrant more of a descending blow (upright swing) and should be played back in the stance. Each player should find their preferred ball position and learn how to measure that distance. You can only repeat the shots if you can repeat the ball position.
For ease of instruction, the ball should be played inside your forward heel for the woods and long irons (2,3,4), and centered between your feet for the wedges and short irons (8,9,P). The other clubs (5,6,7) will be placed in between the two.
Alignment entails aiming your club on the target line, and your feet, knees, hips, arms, and shoulders parallel to the target line. Without proper alignment, one can not make a “good swing” and hit it to the target. You may hit good shots occasionally but a good swing would hit the ball where you are aimed.
Alignment is a major cause of swing flaws. Most people think that they are aimed properly and will make accommodations in the forward swing to hit the ball at the target. If you feel that your alignment is out of place, seek a PGA professional for advice.