Clean up any existing mold on the window to keep it from spreading. Remove curtains or blinds, cover the flooring and remove or cover any nearby furniture before you start to clean. Use gloves, a cotton mask and goggles, and scrub the mold with a mild detergent. Call in professionals for an area larger than 10 square feet.
Wipe up any wetness or condensation that appears on your windows.
Crack a window to improve ventilation if you notice the windows fogging up or condensation forming.
Replace leaky windows or seal small leaks with window caulk or weather stripping.
Use exhaust fans in rooms where humidity runs high, such as bathrooms, kitchens and laundry rooms.
Make sure vents from your dryer or a gas stove are venting to the outside, instead of the inside of your home. This adds to the humidity and may increase condensation.