There are some specific methods that can help you growing taller faster at the age of 15.
Here are some useful methods to grow taller faster:

sleep well

Getting a full night’s sleep every night is one of the things that you must do if you want to grow taller.
Get 8-9 hours of sleep each night and take whatever steps you need to ensure that your sleep is uninterrupted as much as possible.

You should also know that the first 2 hours of sleep are when the most growth hormone is released into your system from your pituitary gland. Not getting enough sleep can lower the amount of growth hormone your body produces, which is not a good thing.

You need to eat the right foods

It’s very important to eat foods that are rich in proteins.
for instance:
milk, fish, eggs, and lean meat are all forms of good protein.
You should also eat foods that have plenty of amino acids and vitamins.
On the other hand you must know about some of the biggest threats to your growth potential: caffeine, junk food and refined sugar.

Leg lengthening, spine lengthening and other exercises

Doing the right exercises can be really helpful for growing taller. Swimming for example can help a lot to increase your growth potential.

In the water you have less gravity and that means more open bone areas for your body to fill them with new bone tissue. The free motion of swimming is very light on your body and greatly releases stress, which can be very bad to your growth potential. Swimming about 2-4 times a week it’s highly recommended if you can.

Anyhow, don’t go out and buy those "wonder pills" that you can find anywhere online, they just don’t work and you will waste hundreds of dollars for nothing. Why not? Well because the only scientific way the body grows is through the release of our natural height increasing hormone called human growth hormone or HGH for short.

There are very few programs that actually work and can help you growing taller naturally by 2-4 inches in a short time.
Check this article for information about hot and new grow taller program that helped many people to increase their height naturally even after puberty:

http://www.squidoo.com/How-I-Grow-Taller-Secrets-Review

Another great way to become taller is to buy height increasing shoes that makes you taller imperceptibly . This kind of shoes will not make you grow taller but it will easily increase your height immediately. For useful information on elevator shoes and how to choose the right shoes that will be the best for you check this article:

http://www.squidoo.com/shoes-that-make-you-taller

All the best.