When it comes to good shooting form, esepcially in a prone or sitting position, try to use your bones as support, versus using your muscles. A good supportive position will greatly help you shoot. For example, if you're sitting indian style, try to get your elbows to be supported on your knees. If you can take a breath and close your eyes, then open your eyes again and you're still on target, that's when you know you are in a good shooting position. You can also use your sling to support your shooting position.