I think looking back at the times I have been able to successfully persuade someone into purchasing an item I enjoy or that I recommend highly, I think have been when I approach them with a friendly tone, I don't immediately try to sell them the product, rather I try to get to know them and see if they fit the product or they fit whatever it is I need to sell, whether that is insurance or I make a product. If it's a great fit, I don't see why they would be opposed to purchasing it, but I feel you are most persuasive or one can be most persuasive when they are not actively trying to be.