Only buy fresh bread not wrapped in plastic.

Only buy fresh bread not wrapped in plastic.
As soon as you feel a cold coming, ask yourself: what did
you eat recently that might have been moldy? Cold cereal, hot
cereal, bread, crackers, cookies, rice, other grains, fresh fruit,
store bought fruit juice, nuts, syrups, pasta, honey? This takes up
a large part of any person's diet, even in a single meal. The
answer is yes, no doubt you ate moldy food recently.
So you can't catch a cold directly from some sneezy companion,
or E. coli, or tapeworm stages, or mites. You have to eat
moldy food first. This lowers your immunity, allowing any
Adenovirus to invade your weakest tissues. If that happens to be
your respiratory system, you get classic symptoms. (Those same
“cold” symptoms can be caused by bacteria, for which I have
preliminary evidence of arriving in a similar fashion.)
As fascinating as this whole story is, the bottom line is: how
can you stop a cold, in record time?