If you have a basement then you will know all about mould and mildew. The key to reducing mildew is to close all windows and vents and use a dehumidifier to keep the moisture content of the air down to a minimum. Also keep an eye on the drainage system around the outside of your house to make sure that no water is seeping into the basement.
If you do not have a dehumidifier then charcoal will absorb the moisture that mildew needs to survive. Place a container filled with charcoal briquettes in the area that is prone to mould and mildew.
Also to eliminate mildew, dust and odors, wipe down walls with vinegar-soaked cloth.