I think that one of the key points is to make sure that arrow is directly below the pupil of your eye. When it is, your left/right shooting will be pretty much on as long as other points of your form is good. To get it just right, try experimenting with your anchor position, the cant of your bow, and the sideways tilt of your head. When you feel comfortable with this practice keeping it consistant. As far as the up/down position, you may want to try gap shooting until you get good and consistant. There is a ton written on gap shooting, so I really won't get into it. After you become good, the gap shooting will become second nature so you really won't have to think about the gap.
I shoot more of a Hill/Ferguson style of keeping the arrow in my periphal (secondary) vision. This works well after you become good with the gap method.