Sudsing up kills germs as well as removes the dirt under which they hide, so be sure to wash often, particularly after touching anything that's been handled a lot -- pens, doorknobs, remotes. Doing it right means lathering for at least 20 seconds (about as long as it takes to sing "Happy Birthday"), and getting between your fingers and under your nails. Rinse thoroughly, and dry -- germs stick to skin more easily when it's wet.
Alcohol-based hand sanitizers can work in a pinch, but won't,remove dirt as reliably as lathering with soap and water; look for a sanitizer that's at least 60 percent alcohol, and be sure to rub it all over your hands as if you were washing them.
"A brisk daily walk is the single most powerful thing you can do to prevent illness," says David C. Nieman, DrPH, director of the Human Performance Lab at Appalachian State University, North Carolina Research Campus. Nieman found that people who exercised five days a week for 20 minutes or more reduced the number of days they were sick by 43 percent.
What's the power of exercise? When you get your heart rate up, cells that fight infection circulate through your blood, and stay active for about three hours afterward. "Anything that gets your heart pumping and your lungs working activates those immune cells," Nieman says.
When you feel constantly anxious, levels of the stress hormone cortisol skyrocket, which can dampen your immune system, making it harder to fight off a virus. In fact, research has shown that people who are coping with lots of stress have double the risk of getting sick.
While you can't control what stress comes your way, you can control your reaction to it, and that's where the protection lies: One study shows that people who incorporate regular meditation into their lives (along with exercise) have a 40–50 percent reduction in respiratory infections.
There's no one magical nutrient that keeps you healthy. Rather, it's getting a good mix of vitamins and minerals that works best to strengthen your immune system. "The nutrients and antioxidants in produce all work together to promote good health," says Marc I. Leavey, M.D. "And that combo can't be replicated in a pill."
To get your daily dose, have one or more fruits and/or vegetables at each meal. For example, try blueberries and bananas at breakfast, spinach leaves and tomato on a sandwich at lunch, carrots dipped in hummus for a snack, and roasted broccoli at dinner.
That's the sweet spot: Research shows that people who average less than 7 hours per night are almost three times as likely to get a cold as those who average 8 hours or more. "If you're run-down, it's a stress on your body, and that can suppress the immune system," says Neil Schachter, M.D., professor of medicine at Mt. Sinai Medical Center in New York. To rest best, turn in at the same time every night, and don't forget your wind-down routine: 30 minutes to an hour before bed, do something relaxing like reading a book.