The Art of War,look at the tactics in this book. They are used by the military to a very good extreme.
I seen President Trump use these tactics since he got into office. Almost to the letter.
I use them to evaluate potential problems. Body movements,eye contact, talking and staring at others.
My favorite is in a restaurant,I tone out noise and listen to others and read lips. Why because it’s fun.
Evaluation of dates male female dates,just to see who’s interested and who’s not.
A phycology class from college helps also.