Lots of good advice on here.
DD is mixed race and has long curly hair. She is only primary school age, so I still take care of her hair, but I'm trying to teach her to take care of it herself for the future.
We wash it once a week with a mild shampoo (the Body Shop rainforest one is good, no nasties).
Condition it but rinse out the conditioner (curly girl method doesnt work on her hair at ALL).
Comb out with a tangle teezer when wet, rub a bit of shea butter or coconut oil in the dry ends, then either plait while wet or leave to dry naturally for curls. To be honest, she wears her hair plaited mostly and just has it out for special occasions, as it is much easier to manage. Loads of good tutorials on You Tube if she wants to learn how to braid her own hair.
She sleeps on a 'silk' pillow case and wears a hair wrap/sleep bonnet if her hair isnt plaited.
Trim it regularly, too. Its made a big difference to the tangles.