There is not any place in the book where it straight out says "here are three steps of the way I trained Frightful. But Sam does talk about various things that he does to train the bird.
For example, the first thing he does (so maybe you could call it the first step) is simply to talk to Frightful and touch her a lot. He says that this makes a falcon easier to train.
Then, in the chapter entitled "Frightful Learns Her ABC's," Sam starts to train her more "formally." For example, he would put a leash on her and let her sit on a stump. He would back up, hold some meat, and whistle to her. That was supposed to teach her to come when he whistled.
The third step that I'll talk about is when he trains her to attack a lure. He made sure she was really hungry, let her go, and then he would throw his lure up in the air for her to swoop down and catch it. That taught her to attack prey, bring it to the ground, and wait for him to come and reward her with food.