Hi! The way that I do the hair on my dolls, is:
I crochet a head cap in a spiral, and sew it onto the head. Then, starting at the center of the head cap, I make huge backstitches (leaving tall loops, however long you want the hair) in a spiral using the spaces between rows, all the way out to the last row of the head cap. Then, I tie off the end, cut the loops, and give a haircut/style. The benefit to this method is that you can manipulate the hair in any direction you want, instead of having to set it in a permanent direction. The only downside is that the hair can be very thick, but skipping stitches/rows and doing less loops can solve that.
I hope your finished product comes out just as you imagine it!