All people have abilities, hopes, and talents that, however warped, can be used for the good if they are motivated in that direction. All people are motivated by selfishness. Remembering this helps us with being realistic when we deal with others. It should also teach us to be cautious about our own motivations in things that we do. Being selfish as we are, we must be accountable to those outside our circle.
People compartmentalize their lives.
People often see themselves as a combination of their different roles. Often people who are doing bad things in one area, have a good image in other areas. Discover what language people understand. If you ask people for too much, or ask them too often, you might scare them away. Give people a chance to look good.