Accuracy and ball saving have got to be the top 2 for me. When I got my first pin, a Comet, I took the glass off and would routinely place the ball to come down to the flippers and just try make the same shot over and over for a while, then move on to other shots. It was a big help over my first set of scores. GRACEFULLY nudging the machine is clutch, draining all 3 balls in under a minute leads to low scores :p