Divots are nothing more than strips of earth dug up after your club hits the ball. You might think it's silly to put so much emphasis on what you do to the ground. But if you take a good divot after you hit the ball, that's proof you made a good strike.
Address the ball as you normally would. A short iron is the easiest club to use when learning to take a divot. With a short iron, the ball will be in the middle of your stance. Put your weight slightly more on your left side (if you play right-handed) with the shaft tilted forward slightly. Your knees should be slightly flexed and your hands should be a little bit in front of the ball.
Keep the club on plane during your swing. Forget complicated techniques – all you need to do is make sure the butt of your club points toward the ball on the takeaway and on the way down. You can check this during your practice swing. Simply cock your wrists halfway into your backswing – about waist high – and make sure the butt of the club points toward the ball. Do the same halfway into your downswing. If the butt of the club points toward the ball, the club shaft is on plane.
Strike down on the ball. Too many players straighten up when making their downswing. If so, you're trying to hit the ball too hard, tensing up and straightening your legs and back. Your knees should remain slightly bent throughout your entire swing. This ensures that you keep turning your body through the bottom part of your swing, so you make good contact with the ball.
Hit the ball first on your downswing. The ball doesn't need your help to get up into the air. By making a downward strike and hitting the ball first, you put backspin on the ball; that makes it go up into the air. After you hit the ball, the club continues to go down toward the ground. Since you're turning through the shot, the club will hit the ground in front of the ball and take a divot.
Finish your swing. Don't just stick the club into the ground. You want to make a good turn through the ball. You'll slice out a nice divot. Its size will vary, depending on how hard the ground is, the slope you're on, and other factors.