Marble is a porous stone and any stains must be removed before they get absorbed.
Coffee, red wine or tea stains
Scrub the stain with peroxide mixed with water. If the stain persists, cover it with salt and let it stand for a few minutes. If the stain is very stubborn you may use a brush.
Ink stains must be removed with ammonia.
Candle wax stains
It must be removed with boiling hot water and then scrub with a clean cloth and linen seed oil to protect the marble and add shine to it.
Marble in the bathroom
Stain resistant marbles must be used in the bathroom. They must also be water, humidity and steam resistant. Italian marbles are best suited for this particular use because of their resistance and because they are less porous.