My rule of thumb is if I am getting to the pocket but not carrying I try to watch the ball's reaction and see if it is burning early and leaving flat 10 pins or over hooking and leaving solid back row pins.
If the ball is burning early and not finishing strong enough I move into the oil at least 4 boards with my feet and 3 with my eyes at the arrows with the same ball and get it out to the same break point with a little more side rotation, if the ball doesn't turn the corner I go to a less aggressive cover and snappy pin over fingers drilling, this usually works.
If I am leaving solid back row pins I move in again 4 and 3 and play the same break point this usually gives the ball enough room to lose some of it's energy and carry out the back row pins.
If I am not finding the pocket and the place I bowl at there are many nights like that I try to change my release and go more end over end with it and go more direct to the pocket, sometimes this means I have to play a shot similar to the one Barnes was playing on TV
yesterday by playing across the third arrow and only getting the ball out to 12 or 13.