1. Themost efficient way of increasing these levels are by human growth hormone injections, but these are illegal if you don't have a prescription, and can cost vast amount of money so i do not recommend this method

2. Drinking milk has been shown to help you grow taller, not because of the calcium intake (calcium has no affect on height), but because in America they inject different hormones into cows - this increase in hormone levels was not seen in other dairy products, only milk. Semi skimmed milk is the best option, as this has the least amount of estrogen in (causes closure of growth plates)

3. Resistance exercise (lifting weights) increases Human Growth Hormone (HGH). This is the most widely known method for improving growth hormone levels and is very effective. Extra muscle will also help you look more attractive.

4. Intense sprinting exercises also causes a burst of HGH (human growth hormone) and also improve HGH even while you are not exercising. In fact, any high intense/anaerobic exercise will help you be taller.

5. Niacin supplementation. Niacin is also known as vitamin B3. in a study, people given roughly 500mg (about 5 pills) of niacin experienced massive increase in growth hormone over two whole hours. NOTE: Only take on an empty stomach, as sugars + fats decrease HGH production

6. Lower your stress. Cortisol is produced during stress which hinders your chances of being tall. Vitamin C lowers cortisol, so if you get stressed a lot, consider taking vitamin C supplements. Growth plates have an ability to have catch-up on growth after a period of cortisol excess - only long term cortisol levels will have a significant effect on being tall.

7. Get at least 8 hours of sleep. This should be mostemphasized as this will double all your efforts.No or little amounts of sleep mean no growth at all!

8. Speaking of sleep, take melatonin. Melatonin is one of the best natural supplements for increasing growth hormone - this crucial substance is a sleep hormone produced by your pineal gland in response to darkness. Melatonin is also synthesized and sold as a sleeping aid, your body produces little amounts of melatonin compared to supplements. However, it can also increase growth hormone, according to a number of studies. Melatonin reduces somatostatin, a HGH inhibiting hormone which will increase your chances of being taller, especially during sleep.

Source: http://articles.pubarticles.com