The best way to clean and polish your diamond at home is fairly simple. If you decide to do this at the sink, make sure the sink is stopped up and for extra precaution, place a washcloth over the opening. Or you can just use a bowl. Use warm water, not extremely hot nor cold. Then add some mild detergent in the water. Dish or laundry detergent can be used. Stir the water around so that the detergent is mixed in and then place your diamond within the water.
Let it set for a few minutes. Diamonds, especially on rings collect debris such as hair spray, lotions, and other grim that your hands come in contact with. Using only a soft bristle toothbrush, carefully clean around the diamond both top and bottom. Remember to only use a soft bristle brush. Stiff bristles can scratch the metal on the surface. After all angles of the diamond is clean, then you need to rinse it with warm water. This rinses away any traces of grim and cleaner on the diamonds surface.
Next you get a lint free cloth and begin drying it. This helps polish the diamond and the precious metal it is set in after its been properly cleaned.