How undercover cops get made just by the way they look at people.
The spotlight effect: why we all overestimate how much other people notice about us, and how we can use this to our advantage when trying to spot a lie (or not get caught in a lie ourselves).
What Jack has to gain by making minor mistakes deliberately when he's teaching a class.
What people are really telling us when they're angry, and how we can stealthily defuse them before they go off.
If you make people feel good about themselves, they will seek to be around you to get those feelings again.