In addition to staying away from people (not always possible, but at least try not to get real close to school age children), and keeping hands and fingers away from your face...
Wash hands frequently in case you forget to keep fingers away from your face
Raw garlic. It's an anti viral, antibacterial, anti fungal. But only real, raw garlic.
Try not to use real money if you can help it. I have debit and credit cards...haven't had to use real money in ages, and that, along with raw garlic, has kept me from catching a cold, whereas before I would get one each year, and sometimes it would turn to bronchitis.
Keep the screen of your iPhone, iPad, etc., clean.
And of course, it goes without saying that we should wash our hands after using the bathroom (especially PUBLIC bathrooms!) but don't wash your hands and then use your clean hand to turn off the faucet and then use it to open the door when you leave. Use a paper towel to turn off faucet, dry your hands, then use another paper towel to open the door. Or your sleeve, if there is only an air dryer.
Our hands are like the fast track for germs to infest us.
I may be somewhat finicky about my hands, but I really really hate getting sick and am not a good patient. 
ETA: I also do saline nasal rinses. They keep the nasal passages moist, and in the event you DO get a cold, they are excellent for clearing out tons of mucus
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