This is the closest you'll get to a tutorial from me xD At least for some time, I'm not ruling it out all together. (and this was a free hand sketch in a sketchbook so slightly different from my portrait drawings on Bristol)this is a close up of a finished drawing, you can see by clicking here
1. Drawn with 0.5mm HB mechanical pencil. Completely free-hand (I used a reference, but no grids, just draw what I see). It roughly outlines where the lines will be, and I use a little rough shading to highlight the areas which will be shaded darker (I made the hair dark at this stage to prevent it looking stupid, it would normally just be left as a line drawing too, or slight shading).
2. I abandoned my HB for a softer 2B 0.5mm mechanical pencil. Refined the lines, correcting them a little where needed, into what will be their final positions. Added more extensive shading of the darker areas to give the face a little depth.
3. Using stumps and/or tissue I blend the rough lines made previously to get smooth skin tones. This is where smooth paper really helps, this is in a Moleskine sketchbook which is great, I also use Bristol extra smooth which is awesome. I also add a little more dark shading and blend again to keep the shape.
4. Between 3 and this final image (after adding the dark hair) I used an eraser pencil to bring out some highlights and blended, then added more dark and blended. Then just repeated this, adding light and dark and blending until I was happy with the tones and contrast. It is now almost done. At this point if the skin had more texture then I would add final details, either light with an eraser or dark with a pencil. This is also when I added the shines in the hair and the little loose fly away hairs that go over the face. Then I'm done!This is a pretty similar process for all my drawings, though for my 'proper' portraits I normally start with a grid to ensure I get the proportions and positions spot on.