Summarize the following:
Although a good pitch requires your whole body to work fluidly, you can train specific parts with particular drills. A good drill to do that focuses on your arm action during a pitch are knee throwing drills. If you are right hander, kneel down on your right knee and pitch the ball to a friend from this position. For lefties do the opposite side. A stiff wrist is an important part of what it takes to throw a good forkball, but this can be a tricky thing to practice on its own. A good way to focus on the wrist is to hold up your pitching arm so it is bent at the elbow and the forearm is vertical. Hold it just below the wrist with your glove hand. Keeping your arm in this position, practice throwing the ball with just your wrist and fingers. To try to put it all together, you can practice pitching against a wall. If you mark a target to aim for you will be able to see how much you are managing to get your pitch to bottom out late on. If you have the equipment, you can film your practice pitches to observe in slow motion how your action looks and what sort of movement is being produced on the ball. If you are struggling with balance, practice holding your balance position, with your front leg raised and your pitching arm back, for a few seconds before pitching. Probably the most fun way to do any pitching drill is with friends. Play catch, and throw in some forkballs to try to catch each other out. If your friend is deceived by the ball as it drops down at the last second, you know it is coming along nicely. It's good to practice with a catcher as they will be able to give you good feedback on the flight of the ball. You can ask a friend, parent or coach to observe your pitch to see if they spot any problems that might be holding you back. Remember, this is a pitch that is very hard to master and can lead to injuries. Take it easy with your practices and stop if you start to feel pain in your elbow, wrist or fingers.

Summary:
Concentrate on your arm action. Focus on keeping a stiff wrist. Practice the pitch against a wall. Practice with friends. Don't overdo it.