An effective way to clean granite counters is to wipe them with a soft cloth and a mixture of water and dishwashing liquid. Avoid using abrasive and acidic cleaners, as these can damage granite countertops.
Water and dishwashing soap is effective for daily or weekly cleaning. To avoid stains, wipe up spills as soon as they occur. If a stain does happen, use a baking soda mixture to clean it. For a water-based stain, use a mixture of baking soda and hydrogen peroxide with enough water to make a paste. For an oil-based stain, use a mixture of baking soda or flour, dishwashing liquid and water. Spread the mixture on the stain, and leave it for several hours or overnight.
Wash the mixture off, and then rinse and dry the counter completely. Avoid cleaning granite counters with vinegar or ammonia cleaners, as they can dull the surface, and never use abrasive cleaners, which can scratch the surface and cause permanent damage.
To protect granite counters and help prevent stains, they should be re-sealed every six months to a year. To test whether it is time to re-seal a granite counter, splash some water on the most used areas. If beads form, the counter is fine, but if the water runs, it is time to re-seal.