Practice the art of observation by engaging in some people watching. Spend an hour or so at a park or a mall or some other area frequented by people and write down what you observe. This trick can help you not only with describing appearances in more detail but also with writing dialogue and exercising your imagination. When you’re writing your visual descriptions of people, try to be specific about what you see (hairstyles, types of clothing, the color of a person’s hat/glasses/bag, etc.). If you’re listening to conversations (without eavesdropping, of course), take note of accents, pronunciations, inflection, tone. Also pay close attention to what people are doing—their expressions, gestures, body language. What might these various things reveal about a person? What might the people be saying, feeling, or even thinking? Make up a backstory for a person or people you see and use this as a future character sketch.