Since you are twenty years old, you have plenty of scopes to enhance your height since growth harmone works up to 23 years for males. You need to observe the following simple rules for the further elevation of height.
1) Take adequate sleep say for eight hours in the night so that the growth hormone works properly.
2) Involve your self in some physical - exercises for at least 45 minutes on daily basis such as brisk walk, cycling, jogging etc.
3) Stretching exercises if done regularly will yield a positive result in the long run.
4) Take care of your diet and include fruits like Apple, Banana, small amount of dry fruits like Walnuts, Cashews, Almonds etc apart from supplementation of Milk, Curd, Cheese. In this context, Carrot - soup would also be benificial since the same contains essential nutrients and vitamins. Protiens would also an vital ingredient to raise your height. You may add eggs and prepared chicken in your meal.
5) Involve in yoga or in meditation for sometime daily in order to alleviate your stress. This works best in raising your height.