Stance at the table is very important unless you are comfortable and having placed your body in proper alignment you will miss continually. Aiming at snooker is like aiming a gun the eyes need to be over the cue running straight down it and not by twisting your head across the line like many club players.
Your aiming point on the object ball needs to stay at that point until the shot has been completed and I mean that the cue action has completed and not during the shot. Moving your eyes during the shot also moves your body so keep still and focused on the object ball.