There's nothing you can apply to your hair, nothing you can eat or drink, no pill to take, that makes your hair grow faster.
Eat healthy. People who are bulimic, anorexic, or just eat junk find their hair grows more slowly and may be in poorer condition because of their nutritional habits.
Split ends are the enemy of growth. People who claim their hair doesn’t grow usually have so many split ends their hair is breaking off at about the same rate it’s growing.
Get a trim once every two or three months. Tell the stylist you’re growing it out and want nothing more than the ends evened out and damaged ends removed.
Don't color, tint, perm, straighten, or bleach your hair. This is huge, since even the gentlest products contain chemicals which dry the hair shaft, making it more prone to splitting.
Never use heat to style your hair--not to curl, not to straighten.
Take it easy on tangles--no yanking.
Since shampoo is drying, shampoo only when you need to. Use as little shampoo as possible, and apply it only where the hair’s dirty, usually the scalp part. Lean forward to rinse if your hair’s shoulder length or longer, so the ends get no shampoo on them.
Shampoo immediately after swimming in a chlorinated pool.
Condition your hair whenever you shampoo. Use a product which promises moisture renewal or hair health. Condition it all, even if you only shampooed the scalp area.
Once a week use additional conditioning products which you leave in for several minutes, then rinse out. (Tip: Apply none to the scalp area and the products will not flatten your hair.)
You can expect 1/2 inch of growth per month, possibly more if you're lucky enough to have the genetics for faster growth. (I do.)