Frequent hand washing is your absolute best defense! My daughter loves foaming soap. The rule in our house is "As soon as you walk in the door, wash up."
I make sure everyone gets enough rest: 12 to 14 hours a night for the kids, and as for the grown-ups, well, as much as we can!
Airborne: I swear by it! All of the parents and teachers at my school do as well. Just be sure to get the orange flavor and not the lemon-lime. I strongly believe in the flu shot. My kids get one every year.
Eat lots of fresh fruits and veggies. And when a cold strikes, comfort food can't be beat: chicken soup, 7Up, saltines, Jell-O, grilled cheese, PB&J, tomato soup… It always did the trick when I was a kid!
Keep supplies on hand so you're not caught unprepared. During cold and flu season, we stock up on honey (use a spoonful for a scratchy throat), cold medicine, OJ that's high in vitamin C, ingredients for homemade chicken soup, Sprite and a box of tissues for every room of the house.
One word: NyQuil! NyQuil is love in a bottle, let me tell you!
Lysol disinfectant spray is great stuff, and we always have it during the cold season. Disinfect doorknobs at least once a day, bathroom surfaces several times a day, plus tabletops, surfaces, chairs and toys, all on a regular basis.