Here are a few throwing fundamentals.
1. Always warm up before doing any kind of throwing. Start on one knee about thirty feet away from you partner. Concentrate on throwing to your partner's chest on every throw. Once you feel loose, stand up and back up about ten feet to continue warming up. Gradually take steps back until you are long tossing. This is the best way to strengthen your arm.
2. Try to bring your throwing elbow above your shoulder when you begin to throw. Practice gripping the ball across the seams when you throw(4 seams). (See Image Above)
3. Use your front shoulder and front foot to aim at your target. Do not let your front shoulder fly up or out. Do not lob the ball unless you are close to your target.
4. Try to throw the ball with the straightest line possible. No Rainbows! A one-hopper is better than a rainbow.
5. Follow Through! Make sure you bring your rear foot around to square up your body. You won't get everything on your throw if you do not follow through.
6. DO NOT THROW CURVEBALLS OF ANY KIND UNTIL YOU ARE IN HIGH SCHOOL! CURVEBALLS WILL DAMAGE YOUR ARM! This is little league baseball. It's not worth messing your future up. Randy Johnson did not throw a curveball until he was 23 years old. He just now retired after 22 seasons in the Major Leagues. He can still throw in the mid to high nineties. It might seem fun to throw them, but you will be damaging your arm.