Persuasion: Universal Principles that Guide Human Behavoir

Dr. Robert Cialdini, Professor of Psychology and Marketing @Arizona State University, has written the most convincing evidence describing the principles which guide human behavior in the context of Persuasion.

In decision making, you would think that one would consider all the possible solutions and alternatives before making up their mind on a decision. In todays environment  the number of choices leads to an explosion of choices and alternatives.

Here are the 6 shortcuts we use to make decisions:
1. Reciprocity
People are obliged to give back to others the form of behavior, gift or service that they have received first.

Examples:
A favor for a favor.
Easiest way to get a smile is to give one first.
A waiter who gives you candy with the bill increases his tips by 14%.
Personalized and unexpected.

2. Scarcity
People want more of the things they have less of.
It's not enough to tell people about the benefits or uniqueness of your product, but also explain what they stand to lose by not purchasing your product.

Examples:
Concord flight sales doubled when it was announced that it was no longer economical to fly.

3. Authority
People follow the lead of credible and knowledgable experts.

Examples:
Physicians display diploma on the wall.
Customer testimonials. Science says it doesn't matter if the person giving testimonial is related or has something to gain from the testimonial.

4. Consistency
People like to be consistent with the things they have said or done.

Examples:
Ask for small commitments prior to asking for a bigger one. Consider newsletters which lead to subscribers purchasing product down the line.
Voluntary, public and active commitments in writing.
When patients write appointment details

5. Liking
People prefer to say yes to people they like.

3 Factors of why people like you:
Similar to you.
Complement you.
Cooperate with you on mutual goals.

Examples:
Exchanging personal information, similarities or interests before getting down to business.

6. Consensus
People look to actions and behaviors of others to determine actions of their own.

Examples:
75% of the guests who stayed in your hotel room re-used towels. Think about how this will affect your behavior.

Employing these costless shortcuts in an ethical manner will considerably increase the chances of persuading someone by your request. 

http://www.influenceatwork.com

Influence at Work is a great resource I recommend you read.