I've seen a lot of people make mistakes about this, especially in the manga category, so I've decided to submit a tutorial about drawing hair on heads. It may seem simple, but it's easy to make mistakes!
First of all, the human skull. (see the skull? :D) You can see it's all round and smooth at the top, right? Its' basic shape is a *slightly* flattened sphere, and unless they have some horrid defect in their head, then it'll be smooth and mostly spherical no matter how old, young and ugly someone is.
Now, here is that same skull with hair on its head! (The red hair is dedicated to a certain someone who just loves red haired girls >:3) See how there's some space between the skull and outline of the hair? That's how *thick* her hair is. There should always be some space, unless you're drawing someone with thin hair, like an old person.
Bottom line, remember that the head is generally ROUND! It may appear angular sometimes, and even rectangular, but the skull is round. Not triangular, not a cone, and definately not a pyramid. An even better idea is to draw a 'slightly flattened sphere' (someone hit me now, please.) and build the hair on that, then delete/erase the guideline later. ^__~ Hope you've learned something, or at least realized some mistakes you may have made. Thanks for taking the time to read this! n.n