Provide advice on how to accomplish the following goal. Give ONLY the advice, no other words or explanation.
For example:

Answer: <advice, as short as possible; a single sentence!>.

Goal: how to remove stains from marble
Mix a few drops of ammonia with 12% hydrogen peroxide to spot clean the stained area. However, be careful when using this method on darker stones as the hydrogen peroxide can lighten the color of the marble.
Use a mild acid solution, such as lemon juice or vinegar, followed by a gentle scrub with a soft cloth. Rinse thoroughly and dry