1. Wash Your Hands
Be sure to wash your hands frequently. Washing your hands is considered one of the most important steps in preventing sickness and spreading germs to others. Also, avoid people with flu-like symptoms an avoid touching your face.
2. Vitamin C
Vitamin C is a powerful antioxidant that protects the body's cells and generates immune cells to eliminate pathogens . Orange juice, broccoli, kale, and kiwi are all rich in Vitamin C.
3. Get Enough Sleep (7-8 hours)
Lack of sleep can greatly affect your immune system. You need to give your body time to recover from the day. If you do not get enough sleep, you are more suspectable to getting sick .
4. Boost Your Immunity With Nutrients
Make sure you're practicing healthy eating habits. I typically drink a vitamin and mineral-packed smoothie every day to ensure my body is getting the right amount of nutrients. Limit the amount of junk food you consume as this is shown to weaken the immune system.
"Research done at the University of Bonn showed that junk food is correlated with a strong inflammatory response in the body, which resulted in an overly active immune system, as well as changes in our genetic coding." 
5. Increase Vitamin D intake
A high dosage of Vitamin D lowers the risk of respiratory sickness and lung infections. I recommend getting adequate sunlight or taking a daily Vitamin D supplement.
"Deficiency in vitamin D is associated with increased autoimmunity as well as an increased susceptibility to infection."
6. Take Pre and Probiotics
Taking daily prebiotics and probiotics may boost your immune system and eliminate harmful bacteria in the gut. Probiotics can be consumed through supplements or fermented foods.
Resveratrol is a powerful antioxidant that has a plethora of benefits from lowering blood pressure to easing joint pain. "Resveratrol can play a beneficial role in the prevention and in the progression of chronic diseases related to inflammation such as diabetes, obesity, cardiovascular diseases, neurodegeneration, and cancers among other conditions." . Grapes, mulberries, and peanuts are all rich in resveratrol.
Bottom line: Be smart and protect yourself and your loved ones. Take care of your health.
Disclaimer: I am not a Doctor or a medical professional.