Use a dehumidifier
Run air conditioning
Open windows when outdoor air is drier
Use exhaust fans in bathrooms and kitchens
Fix leaks and plumbing issues
Dry wet clothes outside or with proper ventilation
Improve room ventilation
Seal gaps around windows and doors
Use moisture absorbers like silica gel or calcium chloride
Keep indoor plants to a minimum
Insulate cold surfaces to reduce condensation
Wipe down condensation from windows and walls
Avoid overwatering indoor plants
Check and clean gutters and drainage
Repair damp walls, ceilings, and floors