Top rollovers are extremely valuable, but they are hard to get to from the flippers, so controlled plunges are key.
If a ball is coming toward the tip of a flipper, you can sometimes just hold the flipper up and let the ball bounce off the rubber below.
Standup target behind center letter "I" is key. Nudge when ball is near the "I" bumper, in hopes of sending the ball up to hit that target.