6 ideas
Items and information seem more valuable when they are rare or becoming less available, because people fear losing them more than they value gaining them and because restrictions threaten their freedom (reactance). Scarcity works most strongly when availability has recently dropped and when others compete for the item, which is why deadline and limited-number tactics work.
People feel compelled to repay any favor, even an uninvited one from a disliked giver, so a small unsolicited gift can extract a much larger return. The same rule governs concessions: when a requester retreats from a large request to a smaller one, the target feels obliged to concede in turn, which makes the smaller request far more likely to be accepted than if it had been asked alone.
In an information-saturated world, people rely on fixed-action heuristics ('click, whirr' responses) that usually produce correct decisions with minimal thought. Because a single trigger feature can set off the whole response, compliance professionals can counterfeit that feature and get assent without the underlying justification being present.
Once people take a stand, they feel pressure to behave consistently with it. Commitments that are active, public, effortful, and freely chosen are the most binding. Small initial concessions (foot-in-the-door) change a person's self-image, so they then justify larger requests, and a person will keep a decision even after the original reason is removed (lowballing).
Deference to legitimate authority is usually adaptive, so people respond to its mere trappings, such as titles, uniforms, and expensive cars, rather than to actual expertise. Milgram's subjects delivered what they believed were dangerous shocks because an experimenter in a lab coat told them to. The defense is to ask whether the authority is truly an expert on this matter and whether they have reason to be truthful here.
People decide what is correct by observing what others do, and they lean on this most when a situation is ambiguous and the others seem similar to themselves. This explains pluralistic ignorance in bystander emergencies: each person reads the others' inaction as evidence that nothing is wrong. The fix is to cut through the ambiguity by singling out one specific individual for a specific task.