Mix warm water and 1 tbsp. of dish detergent in a bucket or bowl. Use more detergent if necessary until the mixture suds.
Soak a soft rag or sponge in the soapy water, and rub the marble statue to remove dirt and grime. Pay particular attention to creases and crevices.
Make a thin paste of baking sodas and warm water and apply this to any particularly dirty areas. Allow it to sit for an hour or longer. Apply elbow grease as needed to loosen grime, but no abrasive cleansers, scratchers or brushes. Rinse thoroughly with water.
Dissolve 3 tbsps. of baking soda in 1 qt. of warm water and mix thoroughly. Wipe this solution onto the marble statue, and allow it to air dry for at least an hour.
Wipe all cleaner away with a clean cloth soaked in plain warm water. Dry thoroughly with another clean towel.
Purchase marble sealant from a stone shop, hardware store or Internet retailer. Read and follow all directions and warnings on the product for proper use. Sealant will restore luster to the marble statue as well as protect it further from stains.
Apply the marble sealer per product instructions; some sealers may require more than one coat to thoroughly protect and restore the marble. Product application and drying time may vary.
Dry the surface thoroughly with clean, dry towels when finished sealing.