Care
Marble may be stone, but it is porous and stains easily. Wipe off anything spilled on marble immediately, just as you would from a wood surface. Use coasters under beverage glasses to avoid moisture rings.
Regular Cleaning
Occasionally wash marble surfaces with luke warm water and wipe dry with a clean cloth. Wiping surface with a damp chamois will not leave streaks. Once or twice a year, depending on soil, wash with a mild detergent solution (hand dishwashing detergent and warm water), rinse and wipe dry.
A light coat of wax will protect the surface of marble but is not considered essential. Use colorless wax. Don't wax white marble as it may tend to yellow it. A marble sealer can be applied to clean marble which will protect from staining and allow soil to be wiped off with a damp cloth.
Special Cleaning
Marble which has become dull, can be livened up by using a commercial marble cleaner and polish. Buy from a company that sells marble. Companies generally carry imported polish-cleaners, which are used on softer imported marbles and hence safe for the harder U.S. marble. They work faster and easier than the old "marble care kits" which used to be distributed by marble companies.
Putty powder, (tin oxide) can be used to polish dulled or etched surfaces, rubbing on with a damp cloth, folding and refolding to clean damp areas, and preferably using an electric polisher for buffing. However it's very hard to find. Severely damaged surfaces, scratched or etched, can be polished by a business making and selling tombstones or other marble products.