Being nice entails curteousness, sometimes talkability and never implying that you might "hang" the person across the counter if you don't get what you want. You just want information.
Playing the fool involves keeping your own knowledge to yourself. You don't act like you know the business that you've come to talk about; you let the person behind the counter tell you. "Oh jayzs I wasn't aware of that" comes in well handy on many an occasion where you realize that you might have an opportunity or an obligation.