Squatting Technique

UPDATE (2020/04/01): Since going to a gym is currently ill-advised and I do not have weights at home, I have been practicing technique using body weight. In order to get the intensity up, I have been doing Arithmetic Progression Squats (APS), which are more commonly known as "death by air squat" . A nice feature of this workout is that the first few sets give time to warm up and focus on perfecting technique. Also, the load on individual reps is low enough that you can sense where you are over-underutilizing a muscle group before an injury is imminent. I have not tried geometric progressions.

A friend of mine told me I was spending too much time learning how to squat rather than just doing it. They are probably right.

Unfortunately, I'd picked up the excellent Starting Strength: Basic Barbell Training, and I was not to be deterred in learning the safest technique to improve strength. Here are some of my notes on squatting:

This is an incomplete summary of the 64 pages(!) devoted to the squat. Which of these did you find intuitive? Which were surprising?