The first step a young baseball player needs to take to get better is simple: throw the ball around. It's easy, it's fun, and it doesn't take much to do. You can do it anywhere. Build up that arm strength and it'll drastically improve your game.
You can never get enough throwing. To be honest, we don’t throw enough as Canadians because of our shorter season.
Kids can be throwing against the walls, they can go to school playgrounds. You don’t necessarily need anyone to work with. You can use Indian rubber balls. Growing up as a kid, that’s what we used to do. You can strengthen your arm that way, and you don’t even need someone to do that with, which helps out.
As a parent, encourage your young ball player to get out there and throw a ball.
Source: http://www.peterboroughsportsxpress.ca