How to learn to draw human portraits?

How to learn to draw human portraits? Drawing is a form of visual art in which an artist uses instruments to mark paper or other two-dimensional surface. Drawing instruments include graphite pencils, pen and ink, various kinds of paints, inked brushes, colored pencils, crayons, charcoal, chalk, pastels, erasers, markers, styluses, and metals (such as silverpoint). Digital drawing is the…