Faith Te specializes in graphite pencil drawings. Visit this demo that includes some of the techniques she uses for her portraits.
Graphite Pencil Portraits
Master American painter, Winslow Homer, routinely started his watercolors with graphite pencil sketches. He then applied the watercolor paint.
Visit: Art Institute of Chicago's Infrared Detail - Graphite Underdrawing
Visit this page devoted to graphite pencil works from the Metropolitan Museum of Art's web site!