There was a fabulous tutorial recently commissioned by the people behind the drawing program Sketchbook and drawn by the super talented Loish. (How I love her artwork!!) While in it she does work solely in Sketchbook, the techniques can easily be applied to Photoshop or a myriad of other programs.
tutorial - drawing a female face by loish on DeviantArt
Here is my sketch after going through it:
This is one of the greatest things I love about being in the digital age. You have so many resources to pluck from that learning is a cakewalk. There are no excuses these days for not furthering your knowledge of your art. Let's do this thing!