All would be a piece of cake (and maybe not so exhilarating to photograph) if subjects simply ignored cameras and went about their business. But we all know that the appearance of a camera causes most people in front of the lens to feel and do wild and crazy things. Children either mug outrageously or hide. Friends and family freeze in their tracks and become great stone faces (I do); or they fuss because you are shooting their worst side, they have no makeup, or their hair is messy. By the time they are satisfied with their own looks, spontaneity is gone and so is your desire to shoot the picture. Simply put, the best shots of people, known or unknown, are often made before they have a chance to freeze or hide.
What if your subjects ask to be paid before they allow their pictures to be taken? If you're in a deprived country, pay 'em. Most who request money are accustomed to being photographed and may cooperate fully, allowing you to pose them. I remember a beautiful Egyptian girl, about 10 years old, who wanted to be paid if I photographed her holding her newly born goat. I was so incensed at being forced to pay that I didn't take the picture. That scene has haunted me ever since. I should have given her the money and made the picture. (An Egyptian friend said: "Look at it this way. Most of us are very poor and the amount requested is very little. At least it is American aid that we will actually get instead of being squandered in administrative red tape.")