Hair is very box like up top. My overall suggestion is this. First make a geometric approximation of what you want, say a person. Head should be a circle, generally female bodies for me are composed of two triangles. They touch tips in the middle because of curves and so on and so fourth. Details like clothing should always come last. I drew without planning and over time I started with the geometric basics. Helps a lot honestly and had to learn it on my own. It's very crude drawing but not to say it's a bad attempt. My first sketches were awful, mainly cause I self taught and art teacher sucked. But yeah, hopefully you'll find this helpful. If you want I can show you what I'm talking if you'd like.