One key to nudging is to remember you move the table, not the ball. You push objects into or out of the way of the ball, not the other way around. For instance, if a ball is heading for the right slingshot, if you push the table toward the right, then you move the sling away from the ball and rob it of some of its energy. If you push the table left, into the ball, you ensure the sling kicks the ball and add some energy.

It may seem like that's obvious, but I've seen a lot of people thinking they are shoving the ball around with their nudges. Telling them to move the playfield not the ball seems to help.