Over the past few years I went on experimental rage with my hair. Growing up as a little girl I always had long luscious curls AND I wasn't allowed to cut it short because as my grandmother always said: "Hair is woman's beauty." So when I got older I had all the freedom to damage my hair by all sorts of treatments. I went blond -> to red -> then black -> then mahogany -> to red and theeen blond again:) after that i did ombre and decided to grow our my natural hair whch is somewhere in between light brown and dark blonde.
I found few things that were effective: first is finding what your hair needs, if you have bleached damaged hair, you need to focus on repairing it. If your hair is not processed but dull and flat, you need to give it moister by choosing a more moisurizing shampoo and conditioner.
Another thing, is what happening inside of your body, eating healthy, drinking water and taking vitamins and supplements. I am a little obsessed with supplements and take it regularly. I tried many and found the best vitamins for growing your hair fast is Maxi Hair by Country Life, I get it of IHerb (its mostly where I get my vitamins and supplements from), use the code GVW130 for some $ off.
Plus there are herbal treatments like spray in vitamins-minerals, oils and hair fertilizers. Essentially its a leave-in mask that you do overnight and rinse in the morning, not the best feeling (aka greasy mayonnaise for your hair) treatment but it helps when you want to grow those curls.