Wipe off any spills and soils that come in contact with marble surfaces immediately after they occur. Marble is hard yet porous, and allowing any liquid to sit on the surface for any amount of time will result in difficult to remove stains on the marble. Use a soft cloth and water. For sticky or stubborn messes, also use a small amount of a gentle detergent such as dish washing liquid.
Clean your marble surfaces regularly with a commercial marble or granite cleaner. These cleaners are gentle on stone, yet effective at removing soils and stains from the surface. Most marble surfaces can be cleaned daily with products such as these. They are available at most home improvement and department stores.
Polish and wax marble surfaces. This will create a barrier on the surface that will help to repel liquids that can stain your marble. Use a chamois to apply a very thin layer of wax to the surface of the marble. After coating the marble, buff away the wax with a separate dry cloth until you have a glossy finish.