How to Add Power to Your Baseball Swing

Steps
Take a small step directly toward the pitcher when you start to swing. Try to keep weight forward to hit more consistant line drives and more homeruns. Also keep length for even more power. Make sure your front foot is closed off when you step. The toes on the front foot should be pointing across the front of your body. If not you are going to spin instead of creating torque as your upper body rotates. Torque creates power.
When you hit the ball regardless of whether it is an inside or outside pitch your hands remain close to your body.The top hand of the bat should have the palm facing up when you make contact. If the top hand palm rolls over on contact you will hit a ground ball every time.
It is important to keep your hands around the height of your chest. If your hands or elbow is too high, you will cut down on the ball and it into the ground. Your elbow should be around a 45 degree angle which allows you to power the bat quickly through the zone.
The follow through is important. Your hands, not the bat,should finish no higher than your shoulder. If your hands finish higher than your shoulder then you are deflecting the ball and not driving through it. Also, try to reach full extension on every swing. Usually done after hitting the ball, but very important.
Watch "Sports Center" in the morning and look at all the monster home runs that were hit the day before. Regardless of how high or how far they were hit , every player finishes his swing with his hands even or lower than his shoulder.

Tips:
Weight training, plyometrics, sprints, are things that can be done in season and off season to enhance strength and power. Stay away from distance running if you want to be explosive.
Practice off a batting tee. In this country players use the tee until they are 7 years old and then start using it again after they are 17. The beginners and professionals use the tee all the time. Scholastic players need to use the tee to develop, maintain,and perfect technique.
You can also keep hands just ontop of the knob as it gives you a little more power.
Using the lower half of the body is a good way to easily produce extra power.
Lead your swing by throwing your hips into the swing, then your hands with follow. That is the new way players are being taught. It is much more powerful. If you think about it, your entire lower body thrusting your entire trunk and arms will generate more power than your jacked up arms alone. Hips will generate more bat speed. Your hips should end up pretty much parallel to the pitcher for maximum bat speed and follow through for power hitting.
If you strike out dont start throwing everything in the dugout, trust me it wont help at all
Swing down on the ball as much as possible, swiming down on the ball will make your bat connect with the middle of the ball resulting in much more power

Warnings
Spend ten minutes doing a dynmamic warmup before swinging 100%. Ask any coach or physical education teacher. You will avoid injury and enhance performance.
Always wear a helmet for safety. You are going to wear one in a game anyway, so you may as well practice with it.
For God's sake, don't do steroids or drugs. You'll be found out and the side effects are huge and you will get in a lot of trouble and sometimes even baned from the game.
Don't use a heavy bat, Ted Willams proved that you don't need a heavy bat to hit the cover off of the ball, use what is just right for you
Don't practice your swing too much or you will get blisters