When it comes to persuasion, Cialdini has literally written the book. He has backed up his writing with years of research.
Here are his six universal rules of persuasion:
1. Reciprocity. People feel obligated to return favors performed for them.
2. Authority. People look to experts to show them the way.
3. Scarcity. The less available the resource, the more people want it.
4. Liking. The more that people like others, the more they want to say yes to them.
5. Consistency. People want to act consistently with their values.
6. Social Proof. People look to what others do in order to guide their own behavior.
Source: Financial Times