Six methods used to influence people to do things that aren't necessarily in their best interest

1. Reciprocity -- People tend to return favors out of a sense of obligation. Influencers exploit this by extending a small favor (buying them a Coke from a vending machine) in order to get a bigger favor back (having you buy a car from them).

2. Scarcity -- When people are made to believe something is rare ("a limited time offer!"), they will desire it more. In Influence, Cialdini writes about an Indian jewelry store that attempted to get rid of a line of jewelry by lowering the price. Nobody bought it even though the store lowered the price again and again. But when a new salesperson misread the price tags and told customers that the jewelry cost 10 times as much, the items quickly sold out.

3. Liking -- People like other people who are members of their "tribe." Influencers seek to find common interests with their victims, tell jokes, and pay compliments. Flattery, Cialdini found, will get you everywhere.

4. Authority -- Influencers who convince their clients, customers, or marks that they are authorities or experts can gain control over them. That's why they hang diplomas (not always genuine) and pictures of themselves posing with famous people on their walls.

5. Social proof -- People are herd animals. They copy each other. When a magazine salesman came to my door a few years ago, he showed me a stack of subscriptions cards that "people in the neighborhood" had filled out. He pointed out that most people bought subscriptions to three different magazines. Fortunately I had recently read Cialdini's book and I knew he was using the "social proof" technique. I didn't buy anything. (And I'll bet most of the subscription cards were fake.)

6. Commitment/consistency -- People like to behave in a consistent manner. Cialdini recounts a personal experience he once had with a young woman with a clipboard who approached him and asked him if he was a patron of the arts. He said yes. She then said she was selling membership to a club that offered discounts to different kinds of artistic events. Cialdini wrote, "I bought the entertainment package, even though I knew I had been set up. The need to be consistent with what I had already said snared me."

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