5 Tricks On How to make the immune system stronger and general personal hygiene tips: CARONAVIRUS - By Reddit Users

Ongoing self-care counts as prepping. Maintaining excellent cardiovascular health, quitting habits that degrade immune system health (alcohol, smoking), practicing good daily hygiene, and investing in our mental health (stress management, addressing anxiety and depression, etc) are tools just as important for long term survival as food, water, and shelter.
 - user orcusamongus

Handwashing is the #1 preventative measure. We used them for everything. At least 20 seconds with warm water and soap. There are videos on how to do it like they do in Medicine. Most people don't cough or sneeze correctly. A tissue is preferred as well as washing one's hands asap. If nothing to cough/sneeze into then the inner shoulder and bend of the elbow is fine. This keeps the germs localized as opposed to spread out in a large area.
Public places with more people have higher chances of infections. Minimally, a surgical mask is ok for the flu but one may feel that an N95 mask is better. If you have neither and you have to get out a handkerchief is better than nothing.
Keeping your distance from those who are sick or potentially infected is a must. With any infectious germ, Isolation and Containment of those who are and could be sick is the priority.
 - user docb30tn

Not sharing cups, glasses, straws, utensils, toothbrushes, eye makeup, makeup brushes, towels, etc., and not touching your own (or someone else's) face are things I keep trying to tell folks are important to promoting and maintaining good health, and they don't listen. Part of the problem is we feel modern medicine makes us invulnerable; the other is folks not understanding germ theory. Prevention is practically a dirty word nowadays (see also: one of the reasons the antivax movement is so prolific), and it is going to come back to bite us in the ass if something doesn't change.
 - user LunaMax1214

I'll chime in here and say that over the counter vitamins and supplements are mostly about as effective as sawdust. The vitamin and supplement industry isn't regulated by the FDA so most companies that make these things dont put any actual helpful compounds in them and often include harmful additives. (Here's a link to an article by Business Insider about it, but you literally can scratch the surface of the internet and find a ton of articles and studies saying the same thing.
 - user belousugar

Cold showers. Whim hoff method.
 - user Secretasianman7