Comment by Jach

Instead of How to win Friends and Influence People, I would recommend Robert Cialdini's Influence: Science and Practice. Instead of just having advice and heuristics most nerds really interested in the problem can often figure out themselves, it describes a lot of experiments and builds a general model for why certain actions work. I think a lot of tricks can be discovered on one's own (sometimes through chance), after all sales people have had a bag of tricks they know to improve sales by x% long before enough experiments were performed to suggest an underlying theory. Having a theory though helps one discover new tricks and predict their effects. You'll also learn some defensive techniques.