Here is the video of the sketching process, you can read below for details.

I start with a grayish background for mid tone and just start sketching the shape of the face.

I didn't really sketch everything in detail because I will leave that for later, but for now I blocked in some of the shadow areas to make the shape more three dimensional.

Next I blocked in some highlights and the basic shape of the hair. At this point I have a better view of what the final picture will look like, so it is good to start make some major changes before its too late such as the shape of the head, position of the eyes and so on.

Than I added some streaks of hair to show the direction of the hair flow.

After you are done blocking in the basic shapes and final positioning of the facial features you can start defining the detail on the face.

In the final picture I brighten up the drawing and even out the tone and added fine streaks of hair.