Use a dehumidifier
Run air conditioning
Improve ventilation
Use exhaust fans in bathrooms and kitchens
Open windows when outdoor air is drier
Fix leaks and water intrusion
Seal cracks and gaps
Dry wet clothes outdoors or with a vented dryer
Cover pots while cooking
Reduce indoor plants
Clean gutters and downspouts
Insulate cold surfaces to prevent condensation
Check and maintain HVAC systems
Use moisture absorbers in small spaces
Keep indoor humidity between 30% and 50%