Alignment is the easiest fundamental to work on, and probably one of the most neglected principles of golf. A good shot is useless unless it is going toward your intended target.
First, you align the clubface square to your target line, and then you align your body. One of the biggest mistakes I see, as a teacher, is when people line up their body to the target first, then set the clubface down. This sequence usually makes people misalign their bodies, causing them to twist and turn inappropriately to get the ball to the target. Do not make the mistake that 90 percent of higher-handicappers do by not taking the time to align the body correctly.
The easiest and most effective way to practice your align correctly is to set-up in an alignment station.
Place a club or alignment rod down on the ground, pointing it parallel to your target. With a secure grip and stepping forward with your back foot, set the clubface down behind the ball with the leading edge perpendicular to your target line.
Then set your front foot into position and adjust your back foot into place so that both are parallel to your target line.
Your feet, hips, knees, shoulders and even eye line should be parallel to your target line. Avoid aiming your body at the target. This closes you off and promotes an inside-out swing or makes you hook the ball excessively. You may even come over the top on the downswing to pull the ball back towards your target.
Practice hitting to targets in an alignment station so you can teach yourself to aim correctly.