T.K.
I asked this same question recently. Here are the responses I got. Some were very helpful.
http://www.mamapedia.com/questions/1359587841641938945
The best thing that is working for us is to 1) find the right balance of products and 2) to not wash it very often, and 3) to keep it twisted, braided, or in 2 side puff ponytails. One ponytail doesn't tame her hair for very long.
I'm using the heaviest moisturizing shampoos and conditioner I can find. Dove, Pantene, and Garnier Frusctese seem to really weigh my hair down, so they are great for her! I am using the Pantene Relaxed and Natural creme leave in conditioner and it is really great. It turns her kinky frizzy hair into thick shiny curls. It looks terrible and is all stuck to her head in the morning from being wrapped up in a scarf at night after she sleeps, but if I rewet it with a spray bottle in the morning the curls snap back into shape. If we don't put her hair in a scarf it gets matted and nappy and turns to dread locks.
A couple times a week, if her hair is down, I put conditioner in her hair and leave it on while she is in the bathtub and rinse that out. I then put another layer of creame leave in conditioner and spray a little detangler in it.
The easiest way to keep her hair from getting matted, nappy, etc is to section it off when it's wet into ponytails all over her head and then braid or twist them. Easiest everyday hair is 2 side ponytails high up on her head.