Brake your wrist almost 90 degrees, so the heel of your hand lays across the bow's handle. Because of this, you HAVE to wear a bracer!! Unlike a recurve, where you hold the bow's grip in the web of your hand between the first finger and thumb, and keep your wrist straight. This is the reason why your draw length shortens with a longbow. Also, cant the bow quite a bit more. I shoot my recurve almost vertical because it's center shot. I cant my longbow about 30-40 degrees. Also, don't hold at full draw. As soon as you come to anchor, pull through and realease, all in one smooth motion. Most important... look at the target!! Nothing else. Bore a hole into the tiny spot you want to hit, and let loose.
Get some books on shooting like: Byron Ferguson's "Become the Arrow", or Fred Asbell's books on instintive shooting. After that... go roving!!! Shoot some stumps, or whatever else gets in the way!!
