I get the fly or colds very often, how can i strengthen my immune system or avoid getting sick so much?

Vitamin/sleep/food: There are many causes that people get recurrent infections. Check with your doctor to make sure you do not have diabetes or another condition that can make you susceptible to infections. If not then eating a healthy diet, doing regular exercise, drinking water and getting plenty of rest are the best things to boost your immune system. A multivitamin daily could be helpful. Wash hands often.