Persuasion is a fickle beast. Sometimes its easy, sometimes not so much.

In his book, Influence: The Psychology of Persuasion. Professor Robert B. Cialdini lists six principles that form the bedrock of the art of persuasion.

Reciprocity: When you give a gift, the recipient feels compelled to give something back. This is often applied in marketing as free content.

Commitment and Consistency: When you make a public pledge, whether orally or written, you feel a strong desire to keep to that pledge.

Social Proof: When other people are doing something, it makes you feel that it is ok to do it too. That is why likes, comments, testimonials, and reviews are so effective at increasing business.

Authority: When you see someone as an authority you are much more likely to do what they say. provided their authority is in the field of interest. One of the most famous examples of this is The Milgram experiment, where participants were told by an authority figure to electrically shock someone they could not see.

Liking: When you like someone you tend to be more agreeable. Pretty straight forward…

Scarcity: When you think there is a limit to something, you naturally want to get it before the supply or time runs out. Whenever you see a call-to-action that says time-is-running-out or limited-spaces-available, the scarcity principle is deliberately being used.

Each of the six principles are powerful on their own, but when used together, they really have an impact. For example, think of the motivational speaker Tony Robbins.

Tony is clearly an authority on empowerment, demonstrated through his authorship of many books and training courses. He is a very likeable individual. He has strong social proof through his countless followers, endorsements, and testimonials. His workshops tend to sell out and the signup pages always broadcast this fact. You can always find free material from his websites. And if you’ve ever been to one of his workshops you’ll know that you are encouraged to make spoken and written commitments.

Of course, these six principles are not the stand-alone answer to persuasion. As Aristotle said, “character may almost be called the most effective means of persuasion.” It is when used in concert with something truly valuable that these six principles do wonders.