Sleep / Get Rest - a weakened immune system generally makes you more susceptible to illness.
Wash your hands often with warm soap and water. Wash for 15 to 20 seconds. It is the soap combined with the scrubbing action that helps dislodge and remove germs. When soap and water are not available, alcohol-based disposable hand wipes or gel sanitizers may be used. You can find them in most supermarkets and drugstores. If using gel, rub your hands until the gel is dry. The gel doesn't need water to work; the alcohol in it kills the germs on your hands. More at CDC.
Avoid touching your eyes, nose, and mouth. Germs are often spread when a person touches something that is contaminated with germs and then touches their eyes, nose, or mouth. Germs can live for a long time (some can live for 2 hours or more) on surfaces like doorknobs, desks, and tables.
Iodine-based antiseptics (substances that stop the growth of germs)
Alcohols (wipes or gels with alcohol in them can be used to clean hands)
Try to avoid close contact with sick people.
Stay home if you are sick until at least 24 hours after you no longer have a fever (100°F or 37.8°C) or signs of a fever (without the use of a fever-reducing medicine, such as Tylenol®).
Follow public health advice regarding school closures, avoiding crowds and other social distancing measures.