Noticing the turn
The method has three parts, and this is the first. You can't climb down at the turn if you don't notice the turn, and most people don't, because it's fast and because the next defence covers it. Look at your marks from chapter 1. If you made fewer than you expected, that isn't because the turn didn't happen. It's because it went past unmarked.
What it feels like. The turn has a signature, and it's worth learning yours. For most people there's a small physical drop, a half-second where the ground under the line goes. Then, almost at once, a reach. You reach for a weaker argument than the one you were using, because the strong one just failed. "The roadworks are nearly finished" is weaker than "the second is quicker," and you can feel the step down as you take it. If you're listening for one thing, listen for the step down. When the argument you're about to make is worse than the one you just made, the turn has happened.
What else to watch for. The subject changing to their tone. "There's no need to be like that" arrives at the turn more often than at any other moment, because tone is the only ground left. The volume rising. A sudden interest in a detail that doesn't matter, like which month the roadworks started. A "well, anyway." And the pull towards the phone, to check, which is often a pull to check something you already know.
Name it silently first. For the first week or two, don't try to say anything. Just notice the turn and say to yourself, silently, "that was it." Then carry on doing whatever you'd have done, holding or sliding, and don't judge it. The point is to catch the moment, and catching it is a separate skill from acting on it. Once you can catch it reliably, the next two chapters give you the words, and the words are much easier to say if you've already located the moment they belong to.
Afterwards counts. A lot of turns arrive in the car home, or in bed, or three days later when the roadworks come up. That's still the turn, and it still gets a mark, and chapter 22 is about what to do with a late one. The habit isn't about being faster than your own mind. It's about not pretending the turn didn't come.