I define the shot line as a vertical line that the ball follows from the shot pocket to the point of release. Some players bring the up ball right in the middle of their face (directly in front of their nose) while others bring up the ball in front of their shooting shoulder. Which is correct?
First, determine which of your eyes is your predominant aiming eye. Take both of your hands and form a circle as far away from your body as possible. Now pick a small object on the other side of the room, and look through the circle you made with your hands.
Now close one eye. If the object stays between your hands, your aiming eye is open. If the object moves, your other eye is your aiming eye!
So how should this affect a player's shot? If he's right handed and right eyed, he should bring the ball up the right side of his body. If he's right handed and left eyed, he should bring the ball right up the middle of his body, closer to his aiming eye. Whichever the case may be, once the player has determined his shot line, the ball should start on and travel up his shot line. Even his follow-through should be on the shot line!