Imagine what hour the ball would have to go into the hole if there was a clock covering it, and then draw an arcing line back from the hour to the ball
Breaking putts can only enter the hole in a limited area; by imagining the hole with a piece cut out you can envision the area of entry
Your ball positon should match the low point of your swing, so it changes with each club and depending on whether you want to hit the ball regular or with a special shot like a draw or fade