How to Pitch a Baseball

Steps:
Setup: Wind-up position...Place both feet together standing straight on top of the mound with your toes dangling off the front, and face directly towards your catcher, your toes pointed towards him with your heels on the rubber. Hold your glove in front of your chest, with your elbows resting on both sides of your torso. Stretch position...Place your feet so they face third. The stretch is a faster way to pitch and you can maintain more balance, resulting in more control. Your right foot should be placed against the rubber, with your other foot 1-2 inches in front. This will enable you to get a full rotation with your hips, which will make you throw harder.
Grip the ball for whatever pitch you want. Keep the ball inside your glove while doing this, and don't begin your motion until you have a comfortable grip.
Motion: Make a small step with your left foot to the left. Shift your weight to your left foot, allowing you to lift your right foot and place it beside the rubber (or pivot your right foot into this position, whichever is more comfortable), so that the right side of your right foot is pressing against the mound.
Lift your left leg to the point where your thigh becomes parallel with the ground or higher. Your body should have begun to move with your right foot in the previous step, and at the end of this step your body should be facing third base instead of home plate.
Do two things simultaneously:
Break your arms in a downward semi-circular motion. Your front arm should stay closed and your front elbow should be at a comfortable angle(45-90 degrees). Your throwing hand should face palm-sided towards second base. Ensure that your body stays facing third base through this

step.
Lower your leg as close to the ground without touching it, and then stride outwards. To lower your leg, bend your right knee until your left leg is close to the ground WITHOUT TOUCHING THE GROUND! Don't stride outwards until you have lowered your left leg fully or you will lose substantial power. Your front leg should have a curved "down and out" sweep towards home.
Land your front foot at a closed angle. In other words, if landing your foot pointing at the plate is a 90 degree angle, land your foot pointing at a 75 degree angle. This will get your body into a power position. Your power position is the position where your legs are fully extended with your hips and arms still closed, ready to hurl your arm towards the plate.
Out of your power position, push off with your back foot, and pull forward with your front foot by pivoting from that 75 degree angle into a 90 degree angle. Ensure that you make this pivot BEFORE you swing open your upper body and pull your left arm towards first base. Pivoting early allows you to generate power with your hips, and create more of a whip action for your right arm. The most common mistake pitchers make is to open their arms before their hips, which removes the power generated from their legs, causing pitchers to have less velocity, and increase the stress applied to their arms. Your throwing elbow should be aligned with your shoulder's(horizontally of course) through this step.
Extend your pitching arm as far as you can, and let the ball glide off your wrist. Do not snap your wrist as this can cause injury. Your wrist should not guide the ball, but rather the ball guide your wrist.
Follow through. Extended your arm as far you can and allow your back leg to lift up from the forward momentum, and place it on the mound to get in a fielding position.

Tips
Always keep your head focused on your target.
Throw the ball, don't aim. If you concentrate too much about throwing strikes, it can easily get in the way of your muscle memory, which could make you throw more balls than strikes.
You should use the same pitching motion for every pitch. This will make your consistent, and capable of having better control of your pitches.
Relax. The more you believe in your mechanics, the better you can perform.
Many pitchers make a small ditch in front of the rubber before they pitch. This allows them to have a comfortable hole to place their foot against the rubber during step 3.
Your stride towards home plate is a crucial element that must be mastered in order to succeed. It should not be too short, but not too far either. Experiment with your stride by extending as far you can, and then seeing if you can hoist your body from that position. The limit at which you can do this should be the point where you stride.
Some pitchers like to do a quick hop after their back leg follows through to get into a fielders position, by pushing off with their front foot (like mike Mussina). Experiment with which works best for you.
Another popular error is to dip your elbow when you pitch. Make sure that you go from "picking the ball of the table" straight to bringing your arm parallel to the ground at shoulder height, with the rest of your arm from the elbow down at either a 90 ("over-the-top"), 45 (three-quarters), or 0 (sidearm) degree angle with your arm. If you dip your elbow, you will not get any whipping action from your hips, and will lose nearly all your power.
There are many different pitching motions (including submarine and sidearm), as well as different pitches to throw. Work with a pitching coach to learn which are best for your skill level.
To be most effective, try and maintain a consistent throwing angle for all of your pitches. Some pitchers throw more overhand throwing a curve ball or dip to sidearm while throwing a slider. While this may give you better control or command or your pitch, it can easily tip off the batter to what pitch you are throwing. Having a consistent arm angle keeps the batter guessing.
During the game, pitchers in-between innings often wrap up their arms to keep their arm warm and capable of enduring the force of each pitch.
To alleviate soreness, pitchers do two things. After the game, wrap ice around your arm and chest furthermore, for the next two days after a game, run for 30 minutes. This will get your blood circulating and help push out the lactic acid that built up in your arm, causing soreness.

Warnings
When throwing these pitches, make sure you are under correct supervision. If you throw a pitch improperly, or throw continuously with a major flaw, it could result in a career ending injury.
When warming up to pitch, whether early in a season or during a game, do so by gradually increase your arm velocity. DO NOT begin your bullpen session throwing your hardest, since your arm has to warm up before being able to endure the force once you are throwing your hardest.
Do not overthrow. When your arm begins to feel tired do not try to pitch through it. A tired arm can become a hurt arm very quickly.

Things You'll Need
A Baseball
A Glove
A Mound/rubber
A Target/home plate
A Partner to catch your pitches (at a distance of 60 ft 6 inches at the Major League level or 46 Feet for Little League)
A back stop for any wild pitches that the catcher can't get to
Patience and determination