how to find the line of aim

[pcb]

Hi, can anyone help first of all how to determine what the right line of aim is. my take on it is the line the middle of the cue ball must travel to make contact with object ball contact point furthest from the pocket . we then try to drop the cue on this line as we get down on the shot. or is the line through the middle of the white to the actual contact the correct way to sight the shot ,however i have been told this is wrong because the line of aim is always past the contact point to pot the ball , one final point ,once we find what we believe is the right line of aim , when down on the shot do we look along the cue shaft to make sure the cue is on this line . thanks hope you can help