Influence, by Robert Cialdini, is one of these books everyone should read. It explains how we are influenced and how to defend ourselves against people trying to manipulate us.
There are six principles of influence: reciprocation, commitment and consistency, social proof, liking, authority and scarcity. There is an well-known additional one, self-interest, not discussed in the book.
We use shortcuts to deal with our complicated stimulus environment, these are automatic behaviors that save us the time and energy of thinking. One example is the contrast principle of human perception. It affects the way we perceived two things presented one after another. If the second item is very different from the first one, we tend to see it as more different that it actually is.
The first principle of persuasion is reciprocation, we try to repay in kind what another person has provided us. The reciprocity rule is so strong that even unwanted gifts can trigger the effect of obligation.
The consistency principle makes us fool ourselves in order to keep our thoughts and beliefs aligned with what we have done or decided. To trigger this principle, social psychologist say that the key is commitment. If you take a stand and commit to perform an action, you will be stubbornly consistent with the action, even if it is contrary to your best interest.
By the principle of social proof we tend to determine what is a correct behavior based on what others think it is correct. The effect is bigger when the action is provided by a lot of people.
We are influenced by people we like such as friends, neighbours, attractive people, people similar to us in traits like opinion, background, demographics, life-style, and people that give us compliments.
Authority provides a sometimes valuable shortcut for deciding how to act in a situation. Interestingly, we are often as vulnerable to the symbols of authority, like the title of a doctor or the clothing of a security guard, than to the person possessing that authority.
The last principle of persuation, scarcity, plays a fundamental role in human decision making. People seem more motivated by the thought of losing something than by the thought of gaining something of equal value.