A good plan of attack begins with decreasing dampness and increasing ventilation. Even if your house is relatively new and has properly installed, working footing drains, excessive surface water can saturate the foundation wall, and evaporate to the interior faster than it can be drained away. Check to see if water pools anywhere beside the house during a downpour or period of melting. Moisture problems can originate inside or outside the house, or both. This moisture usually appears first on the inside surfaces of windows, and may also appear around door jambs and where outside walls meet the floor or ceiling.
Closets can also become damp due to reduced air circulation.
Ventilation is an effective and inexpensive means available to you for reducing humidity, and can be obtained by opening windows or operating an exhaust fan as soon as significant window condensation appears. Throroughly dry a damp spot on an exposed foundation wall or floor with a hair dryer. Tape a 12 inch square of heavy plastic over the spot, and check it in one or two days. We have a dehumidifier, but it is in the sump pump crawl space and probably doesn't do much good. If we turn it up very high, it just runs all the time.