Bob Cialdini is a social scientist at Arizona State University and has studied persuasion for many years. His book Influence is a classic that I've used in my university classes. A very readable author, he's written extensively on the topic and has a new book out 50 Scientifically Proven Ways to Be Persuasive. Here's an interview on NPR worth listening to, especially during this election season. I'm getting my copy next week.