How do you persuade?

Do you take the “our product/idea/meme/service/etc is the best and the rest are crap” point of view? Or do you take “I’m an authority on this topic and I’m looking out for your best interests” point of view? Which is more likely to persuade you to change your mind?

Are you also looking to help customers become so passionate about your company and your product that they’ll do a better job of selling your ideas/products/company than you ever could?

How do you persuade someone to change their mind?