Whenever you feel like you might be coming down with a cold, or if you just spent an hour in a classroom next to a sneezer, do this: Thoroughly dissolve a half-teaspoon of Baking Soda in a few ounces of water, and drink it. Repeat every few hours as needed.
To minimize the chance of a cold, take the Baking Soda every morning before breakfast. If you do catch a cold, treat it with zinc products -- they shorten the time that a cold lasts, and they minimize the effects.