This book is a classic, especially for salespeople, yet is still relevant to us all. It offers academically rigorous yet easily understood information as to what makes people behave as they do under certain circumstances. It provides real insight into some key underlying principles that powerfully affect our choices and actions.

Is persuasion ethical?

When asked this question, Cialdini replies that 'persuasion is like dynamite'; it can be used for good or ill, and it can be handled ethically or unethically. He is careful to emphasise how the secrets of persuasion can be employed in wholly ethical ways, which he contends provide the only route to lasting change.

The six universal principles of influence

• Reciprocation People give back to you the kind of treatment that they have received from you.
• Scarcity People will try to seize opportunities you offer that are rare or dwindling in availability.
• Authority People will be most persuaded by you when they see you as having knowledge and credibility on the topic.
• Commitment People will feel a need to comply with your request if it is consistent with what they have publicly committed themselves to in your presence.
• Liking People prefer to say yes to your request to the degree that they know and like you.
• Consensus People will be likely to say yes to your request if you give them evidence that people like them have been saying yes to it.

Establishing trust

Optimal authority is established by a combination of expertise / knowledge and trustworthiness. Clearly, it is easier to establish credibility for the former. Yet Cialdini says that there is a way quickly to establish trust in a context where you are seeking to influence. The secret is to reveal your weakness before your strength. Mentioning a weakness in your case before going on to talk about what's positive may seem counter-intuitive, but it immediately establishes you as credible and trustworthy.

The power of 'but'

Cialdini observes that the word 'but' conditions people to put aside what has just been said in order to give their attention to what is about to be said. Hence the power of advertisements that include the principle of putting weakness first and then using the power of the word 'but'. For instance, VW ran a very successful campaign along the lines of 'we're ugly but...' and Avis 'we're number 2 but we try harder'.

And finally...

Waiters can teach us a great deal about how to be more persuasive.

Many food-servers have found that they receive larger tips when they repeat their customers' orders back to them exactly as the customer said. A piece of research by Rick van Baaren tested the idea that food-servers who match their customers' verbalisations after receiving the order will increase their tip size. No paraphrasing, no nodding, no "OKs" - just repeating back, word for word, the customer's order. In one study, simply by matching their customers' verbalisations after receiving the order, the food-servers at a restaurant increased their tip size by nearly 70 per cent.

"You cannot antagonise and influence at the same time."