I do pretty much the same as Arthur mentioned. Make sure you are lining up that arrow directly below your pupil. It's supper important. Do whatever you have to with your anchor to get it there. I personally like to anchor my middle finger just under my cheekbone, with my index finger on the cheekbone. The corner of my mouth did not work well for me. As long as you are consistant and it feels confortable, find your own anchor. When the back of the arrow is under your pupil, then line up the front with the target and let it go. I also use my peripheral vision to see the arrow. If I actually look at the arrow, I have to let up.

At first, you may actually want to measure the "gap" at different differences. Put a small target up at the bottom of your full target, line up the end of the arrow directly on the small target and let it go. Measure the difference between the Point of aim and where the arrow hits. For me, it is about 20" at about 15 yards. Use this as a reference.