The first step is to open the picture you wants to draw in your image editing program. Edit out the colors. Create lines from important places, like one line under the eye and one line through the month.
Then, you draw the lines on a paper. Be so exactly as you can. It's important to measure the real dimensions. Then, draw the res of the face and take help from the lines. When you are done, erase your lines. Now, start to create shadows and draw details.