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.
Go through your regular wind-up routine, but stop when you get to the kick, holding at your balance point for three to five seconds. Have a friend, coach, or teammate make sure that your leg is waist-height or higher, or have a look in the mirror. If you have trouble holding the stance for five seconds, practice tightening up your abdominal muscles, bending the leg you're standing on and aligning the height of your hips and shoulders.
Your wrist and forearm position with the slider at release is only slightly different than the curve. With your curveball grip your palm is facing you as you bring the ball out of your glove.: Throwing a slider is similar other than your palm facing you, it is slightly turned in. Using your fastball pitching mechanics with identical arm speed and arm slot, release the baseball in front of you.
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.
The slider breaks down about six inches and in by six inches to an opposite hand hitter. A left-handed pitcher’s slider breaks down and away from left-handed batters; down and in on right-handed batters. It appears to be a fastball but breaks at the last minute going about six to eight miles an hour slower than the fastball. It is one of the fastest pitches in baseball.
Don't worry about wrist motion; keep your wrist firm and worry about the angle of your arm. This will maximize bottom-left break if you are a right-handed pitcher. The side of your hand should always face the batter, and your wrist should always finish at your left hip (again, right-handed). Also, try to aim at the left shoulder of a right handed batter, as this is a good aiming spot for the break to be efficient. For more information, you can refer to this article: How to Throw a Curveball.