Faulty alignment can ruin your shot before you swing the club. Aiming the body somewhere other than parallel to the target makes a good swing bad and a bad swing worse.
Examples:
Learning to align yourself properly doesn't require physical skill or years of experience, just care.
Learn What Square Is
You may know that proper alignment means setting your feet, knees, hips, shoulders, and clubface square to the target line. But do you know what it feels like? Maybe not. It's very common for amateurs (and pros, too) to drift or twist themselves unknowingly into faulty alignment positions. That's why it's crucial that your body recognizes how square feels.

Lay a club on the ground
and stand with your feet shoulder-width apart, parallel
to the shaft. Take another club and make an imaginary
address position: knees flexed, bent forward slightly
from the hips, back straight, arms hanging from
shoulders. Without changing your body position, lay the
club in your hands across your knees. Is it parallel to
the club on the ground? It should be. Do the same for
your hips and shoulders; this will show if your body has
a "feel" for setting up square.
Real Shots

Good alignment starts with
the clubface; get that square and the rest of your body
will follow more easily. Begin by standing behind the
ball, on a straight line with the target. To make
squaring the clubface easier, pick a spot-a leaf, divot,
whatever-that's on the target line and no more than a
couple feet in front of the ball. This is your target
during the set-up. Walk around and put the club behind
the ball so the clubface is perpendicular to the target
line, facing the intermediate spot you chose.

Take your grip, then align
your feet perpendicular to the clubface and parallel to
the target line. Once your feet are square, your knees,
hips, and shoulders should fall into place. Check
yourself against the intermediate target and the actual
target, then swing away.
Private Lessons 1999 Times Mirror Magazines, Inc., used under license by GolfServ Online, Inc. Instructional information provided by Golf Magazine.