Okay people. You ask me how do I do my hair? It's not magic! It's not real talent! And now you can do it too if you have the patience. I'm writing this assuming you know a little bit about using the pen tool in photoshop.
1. Make a line.
2. Put a point in the middle of the line.
3. Hold ctrl
(or the mac equivalent of ctrl) and click on the new point, then drag.
4. Close the shape.
5. Make a point on the new line.
drag to match up with your previous curve.
7. Use the handlebars to manipulate your curve however you'd like.
8. Repeat a thousand fucking times and voi la! Pull the 'magic' out of your ass and impress your friends with a wonderful head of vectored hair
I'm sorry if I've disappointed any of you, I'm not amazing. My method is simple, I just have a lot of patience with what I do and love doing it. Although sometimes works like Angelina drive me slowly insane.
: I start off with the lighter shades of hair, and to minimize your layer count use the 'add to shape area (+)' tool. The thinner the strand, the more detailed your hair will come out. Once I've done a lot of thinner, more detailed hairs, I start layering thicker strands behind them, and finally large shapes to fill in any blank areas that I missed. Adding a few stray hairs here and there help your picture to look more realistic. I use colours for hair directly from the photo but that doesn't stop me from changing them around to fit with everything else better.
Any questions? Feel free to note me. If you have no idea how to use the pen tool, I suggest you take a look at Lemon Tea's Vector Guide 3.0
for the basics.