First find your skin colour and put lines to where abouts the middle is (in 512 it's about 250 px)
This skin color is around light orange.

Then get the path tool and make lines of hair that you want,make sure there is enough space for the eyes etc.
Then when you're done select around the box like I did so it's a full selectionand then make curves on the hair by dragging the lines about,just experiment with what you like.
Then just press enter and it will make a selection,then just fill it in a colour that you want the hair to be.

So now I filled my selection and then I made a new layer and I dragged it under my main hair then blurred so it has a shadow effect,only blur by about 20 maximum (On gaussian blur filter),if you do more then it will look bad.

As you see I got a stupid popup from msn ЌЌ
And that I have made my hair brighter,I just like it this way more.
Then right click on the main hair layer and click alpha to selection,then make random parts on the corners (you have to keep the selection on.)
It looks best when you make the edges with a darker colour like I have done here.

Now,zoom in if you like,make a new layer and drag it under the hair.
Use the circle selction tool or hand-draw the eyes outline,I used the circle selection tool,I selected it,filled it with black and then went on select at the top and shrinked it by 1 px and filled that in with white.
Then I copied the eyes layer and dragged it unde the original and filled it with black and blurred it,again,for a shadow-like effect.

Then I did the mouth.
I used a path tool selection just like with the hair for it and then shrinked,filled in with white and then I made the line thing (teeth) on another layer and thebn duplicated it,dragged the duplication under and blurred it,AGAIN,for the shadow effect.

Hope you enjoyed this tutorial,I do admit I copied off corey's head,simply because it's epic.
This head from the tutorial is 100% made by me.

GIMP is free so don't moan that you don't have GIMP,download it.
REMEMBER : Layers are your friends etc (lol) so do every little part of your head on a different layer!