Place your thumb. Place your thumb under the opposite inside seam of the ball. The further your thumb is from your other 2 fingers, the more the pitch will drop. The closer your thumb is to your other two fingers, the more it will slide. If your index and middle fingers are at a 10 or 11 o'clock position, your thumb should be at a 4 or 5 o'clock position.

The pitcher must kick straight up and stay there for a count of 2 and then he has to reach back, while in the middle of his kick, and take a ball out of the hand of the person behind him. This will keep the pitcher from 'slinging' the ball and hurting his elbow, improves his balance point during his windup, and it keeps his hand on top of the ball during his windup.
3. Elbow: The throwing elbow must be equal to or slightly above the throwing shoulder. As soon as the pitcher lowers the elbow below the shoulder, they put additional stress on that arm. The angle of the elbow joint should be no more than 90 degrees. Pitchers who throw curveballs at angles greater than 90 degrees may put additional stress on their throwing shoulder.

Again, a two seamer is gripped a little firmer than the four seamer. A firm grip causes friction, which causes the baseball to change direction, usually "backing up" - or running in - to the throwing hand side of the plate. It also slightly reduces the speed of the pitch, which is why most two-seamers register about 1 to 3 mph slower than four-seam fastballs.

Another property of pitches is their break. Most commonly, that is the difference between their trajectory and that of a ball thrown with the same initial velocity, but no spin. As you may recall from earlier articles in this series, a basic fastball breaks up, while a basic curveball breaks down. A pitcher’s arm angle can modify these motions, so that a righthanded pitcher’s (RHP’s) fastball moves tends to move toward third base, as well as up.

The arm action on this pitch is a little abbreviated at the end. Instead of getting a nice long arc of deceleration and finishing throwing elbow outside of your opposite knee (as with your fastball), you'll want to bring your throwing-hand elbow to the opposite hip. This, of course, shortens your follow through, but allows you to really snap off the pitch.
Launching a great pitch requires good timing, and lots of control during the leg kick. New pitchers tend to fall forward too soon on follow-through, rather than staying on top of the baseball. This balance drill gets pitchers to practice holding their leg kick before full delivery. It keeps the pitcher in a position to maintain control, rather than rushing the follow-through. Slowing down the leg kick will ultimately help a pitcher to deliver straighter, faster balls, with more power and poise.

When you throw the Curveball, you want to cock your wrist at a slight angle while keeping your middle finger high up on top of the ball so that you can roll your wrist downwards when you release the ball (almost like pulling down the string on a window shade). As a result, the Curveball should spin forward as it approaches the batter, giving the Blitzball a great downward movement. In terms of delivery, some people like to come almost straight over the top to get that great "12-to-6" / Barry-Zito-style drop (drops almost straight down) on their curveball, but this is difficult to do. Most people get better results with something closer to a three-quarters delivery for a "1-to-7" break (a pitch that drops and curves to the side). Try experimenting with different release points and arm slots to find the pitch that works most effectively for you.
Naturally, when you do the 1st two steps correctly, this will follow suit.  Downhill means more tilt or depth.  A 2-plane Slider which breaks Down & Away, or Down & In off the plate, does far more damage to hitters.  Its not a side to side breaking pitch.  When you throw the Slider Downhill, hitters will say that they can’t see the dot.  Their frustration builds as they cannot pick up in the spin.  That is because the dot in on the bottom of the baseball.  Needless to say, this is when you will miss more bats.  Obviously, it means MORE STRIKEOUTS & A LOT OF PISSED OFF HITTERS WHO FACE YOU!
A Hall of Fame pitcher famous for his slider was lefty Steve Carlton. Right-handed pitcher David Cone was famous for his slider, which he was able to use many different ways, as was Bob Gibson of the Cardinals. To right-handed batters, Cone would throw it to hook sharply outside the strike zone, getting hitters to chase and miss it. He threw the pitch from various arm angles to further confuse the hitter. Cone's slider was also a strikeout pitch to left-handed hitters, throwing it to curve back over the outside corner and catch the hitter looking. Cone used the slider effectively during his perfect game on July 18, 1999—the final out was recorded via a slider resembling a wiffle ball. In the first game of the 1988 World Series, Dennis Eckersley tried to strike out Kirk Gibson with a backdoor slider, but Gibson was sitting on that exact pitch and hit a game-winning home run. Joe Carter ended the 1993 World Series with a home run on a slider thrown by Mitch Williams. A remarkable slider was John Smoltz's, which would come in looking like a strike and then break out of the strike zone. Brad Lidge featured a slider in his perfect season as a closer in 2008, and used the pitch to strike out the final batter of the 2008 World Series for the Philadelphia Phillies. Closer Francisco Cordero also throws a slider.[citation needed] Other top pitchers to throw a slider included Hall of Famer Rollie Fingers, who used the pitch to win a Cy Young Award in 1981,[1]and Seattle Mariners and Arizona Diamondbacks starter Randy Johnson, whose slider's lateral movement eventually spawned its own nickname, "Mr. Snappy". At times, Johnson's slider was faster than most pitchers' fastballs. Mike Jackson, who tied Paul Assenmacher with the most games pitched in the 1990s (644), also threw a slider. Ron Guidry threw a slider, which he was taught by Sparky Lyle.
For all three variations of the preventative youth pitching drills athletes will perform 2-3 sets of 8-10 repetitions per arm. Athletes need to rotate through this pitching drill with their partners moving from the shoulder portion into the abdominal portion. Rotating positions will act as the rest period for the athletes which is why rotating after every set is important to keep athletes arms and abs fresh for the next set of pitching exercises. This pitching drill is a great way to get athletes shoulders and core warmed up before a game or training session and should be utilized before athletic activity is performed.

Baseball players place a tremendous amount of stress on their arms and the ligaments which control how the arms and shoulders move. By practicing pitching drills which focus on developing and loosening these muscles athletes will be taking a step to avoid costly injuries. By adding core work into the pitching drill athletes will further protect their bodies by building a strong base at the center of their body.
Simply place your fingers the same way you would a curve using your index and middle fingers putting them close together. Thumb and middle finger split the baseball in half as you should do with most pitches.. Keep your ring finger and your pinkie off to the side as they shouldn’’t make any real contact with the ball. Place a little more pressure with your thumb and middle finger as your index finger puts little to no pressure on the baseball.
The key with the slider is to hold the ball slightly off-center (on the outer third of the baseball). Remember to slightly cock your wrist, but don't stiffen it. That way, you can still get good wrist-snap upon release. If your wrist is slightly cocked to the throwing hand's thumb side, your wrist-snap will enable you to have the pitch come off of the thumb-side of your index finger, which, in turn, promotes good spin on the ball.
a slider spins more toward the vertical axis and hence tend to move across the horizontal plane with a slight to moderate downward angle (otherwise it’s a fat pitch, not a slider) L to R from the vantage of the mound for a LHP and R to L for RHP. A great R hand slider will look like a fastball inside to a RH batter and wind up moving away and down from him so the catcher catches it on the low outside corner of the plate and the batter is completely fooled and half way back to the dugout by then after whiffing at it. A curve spins toward the horizontal axis so that the rotation produces downward force (bernoulli) and hence it “breaks” or curves more than “slides”. A great curve will break 12 to 6 or down the face of a clock. A great slider is more 2 to 7 for comparison. Both wickedly effective pitches when thrown in the right count and settings.
I would recommend waiting until the player is 14 or 15 years old. If young players throw curveballs on a consistent basis at younger ages they can cause damage to their elbows and thus hinder the growth process. But it’s not only the fact that they are throwing curveballs at a young age, it’s the fact that they are throwing curveballs with improper mechanics that causes much of the damage. The key is to make sure they are throwing the curveball with proper pitching mechanics.

This is also important for throwing a fastball and other pitches as well.  What do I mean when I say stay behind the ball?   It means don’t be under the ball, too much to the side of it, or overdoing it with your wrist or elbow. Regardless of your arm slot, you will properly get to this point in your delivery by doing everything correctly with your mechanics from the ground up.  From the time your feet first move to deliver the pitch.  
To throw start with your dominant hand facing away from the catcher facing sideways.  Bring up your front leg.  When you do this at the same time bring up your throwing arm with the ball facing away from the catcher 90 degrees to your shoulder like an L shape.  Then bring your arm down to your knee and release at the time necessary.  It should look something like the video.  He doesn't bring his arm and leg up at the same time but everyone's throw is a little different.
In order to master the curveball, you must start by gripping the ball with your middle and index fingers together, with the fingers across the seams of the ball at the widest part (the widest distance between the seams). Keeping a tight grip on the ball, especially with the middle finger, don’t let the ball touch the palm of your hand, or you won’t generate enough topspin, which is what allows the ball to drop when it gets close to home plate.

A slider is the third fastest pitch in baseball. (The No. 1 fastest is a four-seam fastball and No. 2 is a two-seam fastball.) It's important for pitchers, parents and coaches to learn a proper slider grip and to learn correct throwing technique of a slider to ensure and promote arm-health. A slider is gripped like a two-seam fastball, but held slightly off-center.
From the wind-up position have the pitcher rock, turn and raise his leg to the balance position. However, instead of either stopping, or going on to pitch, he now lowers that leg to the ground next to and immediately behind the pivot foot. He should now be standing facing either 3b (rh) or 1b (LH), in good balance before beginning. Now he simply re-raises the non-pivot foot and pitches.
A slider is meant to be slightly more deceptive than a curveball because it is thrown harder and has spin that more closely resembles a fastball — although it doesn't create as much overall movement. Many power relief pitchers possess only a fastball and a slider in their arsenals — with one pitch setting up the other because of the late deception created by the slider.
I learned this pitching drill from Coach Scott Birchler who was a high school coach at our rival high school but as I got older and made the transition from player to coach, he helped me a lot. This pitching drill that he taught me is great for any pitcher who wants to be more consistent with their curveball or slider and fixes two of the biggest problems in guys who throw these pitches, dropping that elbow and not finishing the pitch.