Wash your hands. Avoid crowds. Avoid public places such as shopping malls unless absolutely necessary. Avoid public transportation. Use those sanitizing wipes at the grocery store. Wash your hands.
I average getting a cold about once every 10 years. I spend several hours a day outdoors (in all weather), come in contact with many people in public places and never even take aspirin.
Frankly, I think the body needs regular exposure to germs in order to keep the immune system in good shape. People that go out of their way to avoid germs end up getting sick more often because their immune systems aren't maintained in good shape.
For more proof of my theory, consider two public figures who obsessed over avoiding germs - Howard Hughes and Michael Jackson. Both of these people led sad, pathetic lives and were not in good health at all.
Now that's not to say that we shouldn't worry about hygiene at all but obsessing over it is no solution either.
One of the dirtiest places you can touch are the handles of grocery shopping carts. They’ve done tests of all the germs that are present on shopping carts and the results have been astounding. Be sure to sanitize/wash hands as soon as you’re done touching those things.