Human hair is programmed by our DNA to grow at a certain rate, about 1/2" per month. You can't really make it grow faster than that, though you can make sure it doesn't grow more slowly by making sure you eat a good diet, so that your body has the nutrition it needs. Biotin and Viviscal can grow MORE hair if your hair is thinning, but they don't really speed the growth of existing hair.
If your goal is length then it's also important to protect the hair you do have from breakage. Covering your curls when you sleep, avoiding brushes, and being gentle when handling your curls will help.