Drawing hair has always been my forte and I think it's best to first decide on the level of detail you want. Also, you want to sketch out the head/skull on which the hair will be sitting. I always start with the bangs and hair closest to the face and work my way outward. You have to adjust for the characters movement as well because the hair will flow with whatever motion they're making. To start off I suggest drawing a still person so that you get a sense of how hair falls naturally and then moving on from there.
Studying how other artist do it is a good way to go about it too. Observation is the key to good drawing! My hair styles often consist of high detail, every strand is outlined and shaded according to how it sits. I've also done some less detailed work just to save time. If you want you can check my
DA and see how I've done it
Just remember that it's your picture and you have full creative license over it so you could make their hair completely unrealistic and still make it work for your picture. Just go with the flow of your current project ^^