eat more protein, you need a lot of it for your hair to grow long shiny & healthy, foods with protein like chicken, fish, pork, meat, beans, spinach, nuts and eggs.
drink plenty of water, drinking water is an easy and absolutely essential part of growing longer hair.
-get a lot of sleep
get plenty of sleep, eight hours of sleep is essential, sleep is the main time which your body spends on growth and repair.
-take care of it
get your hair trimmed about once every three months, it's important to get the damaged bits cut off other wise you'll end up with long hair that feels and looks like straw.
don't use harsh chemicals on your hair, the shampoo & conditioner you use may be contributing to poor hair growth, next time you wash your hair, use an all-natural shampoo, read the label and use a shampoo that contains only natural oils and other cleansers, no chemicals.