how to throw a good 2 seamer?

Keep your fingers on the seams at the closest spot between the horseshoes, keep your hand behind the ball as you throw it...a good way to tell if you do that is to put a piece of electric tape around the axis with it going right between your fingers as you throw it, no matter your arm angle, it will keep the line stable (Not wobble). From that you can over balance to one side or the other to cut or sink it.