Start by using a mild, ammonia- and phosphate-free dish soap and warm water to clean your jewelry before using any other method. First, fill a bowl of warm water and add a little dish soap to mix into the solution. Take a toothbrush and dip it into the soapy water and gently start scrubbing the gemstone and sterling silver. Rinse the jewelry in a separate bowl of warm water and dry it off with a towel or cloth.