Drew Barrymore Illustration
Software: Adobe Illustrator CS version

Create New document as per required size. Go to File - Place, browse your image and place it on art board, lock it.
Let's start with face, create new layer and name it face, create a rectangle box according to face size, double click on the face layer. From the option box deselect preview mode and activate the Dim images.

Step 1: Illustration

Next step is creating face mesh, select mesh from tool box, create mesh according to face structure, use Direct selection tool (A) to edit mesh (you should create mesh using rectangle box for the better result).

Step 2: Illustration

After creating mesh work pick some color samples from the face using eyedropper tool. Coloring and Shading you can do either in opacity mode (placing face mesh fit to the original face image) or by placing beside the original image (toggle). Pick the face color and fill on the face mesh, using direct section tool click the mesh node point to apply shading.

Step 3: Illustration

Creating eyes, nose, lips....

Step 4: Illustration

Next step is creating face mesh, select mesh from tool box, create mesh according to face structure, use Direct selection tool (A) to edit mesh (you should create mesh using rectangle box for better result).

Step 5: Illustration

Creating hair is the difficult work .

Create background mesh for hair, and apply lighter, darker shades and color... as per original image.

Download hair brush extension from this link - http://www.adobe.com/cfusion/exchange/index.cfm?event=extensionDetail&extid=1045395.

Draw hair path using pen tool. Coloring, shining and shading all applying using transparency option, Select any hair group, go to window - transparency (Shift+F10), from the option choose soft light, color burn to get shiny effect ( depends upon background color).