Unless you live in a bubble, you will to be exposed to infections. This is actually a good thing in very small quantities. I joke about licking a busy sidewalk with my friends for the reason as I rarely get sick. (I don't recommend that but hey it might just work).
Here are 6 things you can do to minimize your chance of getting sick. 
Vitamin D Your vitamin D levels may run on E in winter and D can spur your body to fight off colds. Taking additional supplants of vitamin D can help a lot. 
Greek yogurt Cold and flu viruses might have an Achilles' heel: Greek yogurt. In a study published in Clinical Nutrition, people who consumed a specific strain of probiotics daily reduced their risk of catching one of these bugs by 27 percent. Aim to eat at least one serving a day of a Greek yogurt with live cultures, suggests Spencer Payne, M.D., an associate professor of rhinology at the University of Virginia School of Medicine. 
Green tea Skip the black coffee and brew some green tea. Its magic ingredient, a catechin called epigallocatechin gallate (EGCG), can damage influenza virus particles and stop them from entering your system, a German study reveals. 
Skip the alcohol Ya I don't even know why I added this one in here but it does have some merit. It interferes with sleep quality, and you are much more likely to get sick when you are sleep-deprived. A little drink-a-link also disrupt REM sleep, which is the most restorative part of sleep 
Protein Make sure to get enough protein during the day. Research shows that diets that are too low in protein can deplete the immune system. So I make sure to get protein-rich foods throughout the day. (fish, eggs, nuts, meat or try Fuel for and quick go to protein drink)
Sweat baby sweat! Exercise is awesome to build your immune system. In fact, it can slash your risk of catching a cold by 27 percent, Korean researchers report. Working out switches on your immune response, possibly by sending a cascade of "natural killer cells" to hunt the rhinovirus. If you are already sick...keep exercising! Exercise stimulates the production of epinephrine, which constricts blood vessels in and around your mucous membranes and can relieve nasal discomfort.