Now, don't get me wrong, I don't consider myself an expert handing out advice, but it occurred to me that I could at least share the system I use for creating faces.
First I start with the basic head shape, if you like, it's a bit like drawing the brain and then building it from there. It all takes a bit of practise and as you can see from the sketches, no two heads are the same. I've written notes on my page, but basically, I divide the face into thirds, coming down one third for the eyes. Then come down another third for the nose and then divide the final gap in half and put a line in for the mouth. The top of the ear should be level with the eye.
By changing the angle of the eye line you can position the head however you like. Play with the features until you find a look you're happy with.