Instructions:
For added effect, go to the edges of the hair and use a soft, nice brush to feather the ends of the locks. There's really no overdoing this unless you totally go mad with it, and if you use a nice, dark colour - some of it will look like nice shadows, and some of it will look like shadowed strands. If the hair is shoulder-long, as it is here, it really breaks up monotony of skin... and if the hair has bangs, please do something similar with the bangs but not quite as feathery - or the hair ends up having a slightly frazzled look.

Common mistakes:
Just leaving the hair blocky. Generally, the edges have already been softened up by now, but even so, give it a once-over just for safety's sake.