I sucked at drawing faces, the only reason I can is because I was in a specialist art course and got to spend 4 months with a facial anthropologist doing facial reconstruction with both clay and pastels, it was one of the most interesting things I've done and really helps you draw faces once you understand all of it. But really, if you spend enough time looking at pictures of faces and looking at the bits of details, you can get it down pact with enough practice.