Lots of vitamin C is the best bet. A cold is a viral infection and short of locking yourself away, there's very little you can do to stop yourself getting colds. Some poeple say don't go out in the cold, or with insufficent clothes on, but this is pap. You cannot get a virus from a temperature!! Since the common cold virus is a mutagenic virus (i.e. like the HIV virus, it constantly changes form), it is as good as impossible to develop an effective preventative medicine - which is why those available are all curative! Your best hope of curing a cold is to ride it out and keep yourself full of nutrients since you need energy to create the antibodies to fight the disease. However, if you get another cold, those anti-bodies are likely to be pretty uselss, since the germ will have mutated again. Grrr!