The most important point of drawing hair is that it mustn't look like a hat. I believe that it is easier when you draw the head frist and add the hair when you finished it. Mark the falling of the hair with arrows that point in the way it should fall.
You can take a fashion magasine and look for the hair styling of the models. There you will see the falling of the hair and you could imagine how you would set the arrows and draw it.