Mold depends on moisture to grow. Mold can trigger asthma and allergy symptoms.
Reduce moisture and increase ventilation (airflow): open windows slightly when showering, use exhaust fans.
Fix water leaks. Renters, report leaks to your landlord.
If you see mold:
Eliminate the source of moisture/water first.
Scrub mold from hard surfaces with soap and water, dry completely.
Avoid using bleach (unless you are cleaning sewage).
Do not paint over mold.
Discard moldy objects (like carpets).
After a flood or water leak: remove wet items and dry the area within 48 hours.
If mold covers over 3ft x 3ft, hire a professional mold abatement company. If you rent, report mold to your landlord. If conditions are not fixed, ask your local building department or code enforcement official to inspect your home for water damage or leaks.
Learn more about identifying and getting rid of mold: