1. Try to get up early in the morning and you will also go to bed early.
2. Do not eat much, do not eat junk food.
3. Drink 10-12 glasses of water daily.
4. Don't take cold drinks much and cigarettes, beer or any kind of drug.
5. You can do mediation.
6. Acupressure may help u to build up your immunity.here is a way-
As you can see in pic. You will press at that point on your both hands.You will press this 1-2 minutes at least 5 times in a day. First time when you will press there u may feel a little bit pain. But don't worry. If u practice this for a week you will surprise to see your immunity.
6. Do pranamaya every morning in fresh air.
These are the ways to build up a strong immunity. These is an ancient Rishis's invention. perform it you will sure to build up strong immunity.