Find the practice.
See it in the book.

“Not long ago, one of the world’s top tennis coaches, a man named Vic Braden, began to notice something strange whenever he watched a tennis match. In tennis, players are given two chances to successfully hit a serve, and if they miss on their second chance, they are said to double-fault, and what Braden realized was that he always knew when a player was about to double-fault. A player would toss the ball up in the air and draw his racket back, and just as he was about to make contact, Braden would blurt out, “Oh, no, double fault,” and sure enough, the ball would go wide or long or it would hit the net.”

“Andrew Pole had just started working as a data expert for Target when a few colleagues from the marketing department stopped by his desk one day and asked the kind of question Pole had been born to answer: “Can your computers figure out which customers are pregnant, even if they don’t want us to know?””