Washing your hands with any kind of soap gets rid of germs, as the soap and water washes them off your hands, even if it isn't killing them.
For those without easy access to a sink, Haller recommends using an antibacterial hand gel, which he says is "just as good as hand washing."
"We'll tell people to keep one with you in your pocket or your purse or your car, when you're going from place to place."
Additionally, when sneezing or coughing, covering your nose and mouth with your elbow instead of your hand can help prevent spreading the flu to others -- as can washing your hands after blowing your nose.
This one is especially important if you share a work space with a number of other people -- any of whom could be carrying the flu virus.
"Wipe off before and after. That way you don't inherit someone else's germs, and you don't leave your own," said Dr. Sandra Fryhofer, a general internist in Atlanta and past president of the American College of Physicians.
Some of the germiest surfaces you come in contact with during the day will be in your office.
So keeping your work area clean may be one of the best ways to avoid picking up something that would keep you home from work.
"When the air outside gets colder, it gets a lot drier. It dries out the membranes of the nose," said Haller.
This is bad news for the mucous membranes, which rely on moisture to trap invading microbes and protect us from them.
The mucus is sent to the stomach, where the acids it produces destroy the invaders.
Because of that, keeping nasal passages moist is an important step.
"Humidifiers can be really helpful," said Haller.
Additionally, in dry air, particles like the flu virus can stay airborne longer. By moistening the air, the water droplets will adhere to the particles, sending them downward.
A study done at the Mount Sinai School of Medicine last year showed that, in gerbils at least, relative humidity and temperature had a lot to do with how much the influenza virus spread.
Haller recommends using a saline solution as well to keep the nasal passages moist. (For a video demonstration of how to do this, click here.)
"Since it's just saltwater ? you can do it every couple of hours if you need to," said Haller.
Even ensuring that you're drinking enough water, Haller said, can help keep the body moist enough to protect against the flu.
Almost always a good idea anyhow, exercise can help you avoid the flu as well.
"Exercise can help boost the immune system," said Fryhofer.
The increased circulation from exercise gets white blood cells moving around the body to help fight off infections.
But exercise may not do much once you have the flu. While people who feel up to it can exercise, as Dr. Lisa Bernstein, an assistant professor of medicine at Emory, explains, most are too tired to exercise when they have the flu.
Keeping your immune system in top shape involves eating right, exercising and getting enough shut-eye.
And flu season is no exception. Getting enough sleep not only helps you avoid the flu, but if you do get it, it may not last as long.
"Get plenty of rest, so if you do get sick, you can get over [the flu] more quickly," said Fryhofer.