
A guide to the psychological tricks that win sales battles, which reveals more than ten keys to subtly elicit agreement from even the most stubborn customer.
"Covert Persuasion: Psychological Tactics and Tricks to Win the Game" by Kevin Hogan http://www.amazon.com/Covert-Persuasion-Psychological-Tactic...
Great book about all-around persuasion techniques , marketing, and also copywriting.
Keep Cialdini's "weapons of influence" in your back pocket when trying to persuade anyone -- but especially when writing your own web copy and/or creating A/B or MVT tests of your web copy. The concept of Reciprocity is one that more 'freemium' startups should be thinking of when trying to monetize.