The best stain remover for granite countertops is a solution of warm water and mild dish soap. Simply mix a few drops of dish soap with warm water and use a soft cloth to gently clean the stained area. For tough stains, you can also use a mixture of baking soda and water to create a paste, then rinse the area thoroughly with water. Its important to avoid harsh or acidic cleaners, such as vinegar or lemon juice, which can damage the granite surface.