The key is keeping the hair moisturize and clean. I am assuming you are black and have natural afro hair (please correct me if I am wrong). I am only saying this because black natural hair is different from the other races hair. It's much drier so a lot depends on keeping the hair constantly and consistently moisturize. This means spritzing your hair with soft water, using oils (like coconut, castor, jojoba oil), using a heavy butter (like shea butter) and leave in conditioner. You also got to protect your hair from the elements (such as the weather) and protecting and limiting your use of heat and harsh chemicals. If possible refrain or limit use of heat (blow dryers, flat irons).
Also be healthy drink plenty of water, exercise and eat healthy. Be good to your body and your body will be good to you
If you are not black or don't have afro texture/coily hair, some of the tips above can work for you too, especially about living a healthy lifestyle, protecting your hair from heat and the elements and keeping it clean.
Lastly have patience. It may take time so don't check your hair constantly, let it grow. By the way I have some hubs on natural afro textured hair so check it out!!! Good luck!!!