Zen Pinball

This should be the first trophy to aim at while playing this table. The reason for this is because the skulls you collect carry on across playthroughs. So, no matter which trophy you're aiming at, first thing you must do on a new game is collect the crystal skull for that game.

The most consistent way I found to get skulls was to perform a triple combo on the ramps. They don't have to be different ramps (you can perform a combo shooting the same ramp over and over) but each ramp must be shot within 5 seconds from the last one so the combo won't end.

Start by shooting the Ryu's ramp. Then the Jump ramp. Then shoot both again. These are the easiest ramps to shoot. You can hit them by letting the ball roll down the flipper and shoot it a little bit before the tip. Also, after the ball goes through the ramp, it'll land on the opposite flipper, allowing you to immediately shoot the next ramp.

Once you shoot each ramp twice, you'll have performed a triple ramp combo and you'll be awarded a crystal skull.

With this method, you can only achieve 1 crystal skull per game. They won't give you more no matter how many ramp combos you perform. There are other ways to achieve skulls, even more than 1 per game, but I'm guessing you won't be done with this table before 30 playthroughs (if you do, grind it up!)