A huge problem with the lat pull down is that some lifters can not isolate the lats and end up using their biceps to do a lot of the work. To isolate the lats, use a wide grip and when youre pulling down, focus on your lats pulling inwards as they go down. Imagine them pulling down in a semi-circle motion.
Its also common for some lifters to lean back and swing the weight down. This is cheating and will not get the maximum results from the lat pull down. Keep sitting upright throughout the movement.
Finally, if you find your forearms are burning out before you finish the set, grip with bar with a "hook" grip. This means you do not place your thumb around the bottom of the bar. A hook grip takes some of the strain off your forearms when performing pulling exercises. Never try to pull the bar down using your forearms. The forearms will simply be used to hold the bar.
Instructions
Set up for the lat pull down by attaching a wide grip bar to the machine, selecting the weight you want to use, and adjusting the thigh pad.
While standing, grasp the bar with an overhand grip at wider than shoulder width apart.
Holding the bar, sit down on the machine. This should take the weight off the stack.
Keeping your back straight, eyes facing forward, and without leaning back, slowly pull the bar down to your upper chest. Do not let the bar touch your chest.
Pause, and slowly lower the weight back to the starting position. Do not let the weight touch the stack.