First,you should take more exercise.you can do sports like running,swimming,or playing basketball.
Second,you ought to eat healthy food such as vegetables fruit and milk.Don‘t eat junk food.You should drink enough water every day.
Third,you must get enough sleep when you may get tired or sleepy in the day.Don't stay up late.
Finally,you should enjoy yourself and stay happy.Being in a good mood is good for you health.
I hope the advice can help you.