Some students have a friend take a profile picture and simply enlarge it on their computer. Then look closely and draw the shape the best you can.
Others with print their profile picture and trace it at a window or a light box.
Some students, simply put the photo into Photoshop and add an adjustment layer turning it black and white. Then add an adjustment layer raising the contrast. They can then cut out drawing, images, and things that interest them and add them to their work digitally.
Take a profile photograph of your friend that is lighted from the back. Print it and trace it. Or place it in Photoshop and create your artwork digitally.