Hair can be difficult, especially if you get everything just right but the hair won’t come together (though this applies to most, if not all, parts of the drawing process). This is the process I usually go through when drawing hair

1. Start with the head shape
2. Outline the shape of the hair, the style you want
3. Using short strokes, go over that and if any hair goes in a different direction than the rest, do it in small clumps
4. Let strands sort of fall in the face
5. Make sure the ends are done in strands and does not just close in one giant clump
6. Add some short strokes in the hair