I keep bottles of hand sanitizer in the car, in my purse, in the kitchen and in the kids' backpacks. We use the handy wipes that grocery stores offer to wipe down cart handles and baby seats. And we avoid notoriously germy places (such as fast-food restaurants' indoor playlands) during the peak of flu season.
Stay home and get better! When my kids have a bad cold or the flu, I don't send them to school. I really think if everyone did that, colds would be far less common.