Is there any right way to throw, such as rotation wise? If not thrown right can you get injuries?

Most people would say there is only one way to throw, and that is over the top. I personally throw the ball three quarter sidearm, and I have no injuries. It really is all about how comfortable you are when you throw. Stretching is important, but not vital, especially if you aren't a pitcher. Some average arm stretches are helpful, just make sure you warm up plenty before throwing full speed.