Things I did:
1. Watch Bowen Kerin (as mentioned) and Keith Elwin videos, other instructional ones like Deadflip work too, but Bowen does a great job in his PAPA videos for general skill demonstrating and strategy.
2. Use multiball to take the dangerous shots (dangerous as in a big risk for draining the ball).
3. Try to score big WITHOUT nudging then work that into your repertoire later.
4. Learn to ball trap on the flippers, especially during multiball. Personally I like just one-timing during multiball but the problem is 2 balls can collide and cause them to drain.
5. play, play and play.