Healthy fats
Make sure you are getting enough healthy fats - nuts, seeds, avocados, olive oil, coconut,...and flax oil is wonderful to help the skin hair and nails so make sure you include that in your diet.
One thing that I do, which may or may not be just another "granola hippie" thing that I do is I trim my hair on every other full moon. Someone told me once (someone with super long hair) that she trimmed hers on the full moon because the gravitational pull is stronger then so your hair grows a bit faster than normal. I don't know if it's true, but I've been doing it for years now and my hair is long and strong and it used to seem like it took forever to grow.