Fill a small bowl with warm water and a teaspoon of liquid dish soap. Gently stir the water to evenly distribute the soap throughout the bowl. Submerge your ring in the solution and allow them to soak for 15 minutes to loosen dirt particles and penetrate built-up oils or residues.
Remove the ring from the solution and use a small, soft-bristled toothbrush to thoroughly scrub it. Focus on the pockets around the diamond's setting and any engraving or indentations in the band where dirt may have accumulated.
Cover the drain in your sink. Rinse your ring under the tap to remove loosened dirt particles and soap residue, which can give jewelry a dull, flat appearance.
Buff your ring gently with a soft, dry cloth to polish the metal and prevent water spotting. For extra shine, finish with a special chemically treated polishing cloth, available from most jewelry retailers.