Store individual pieces of jewelry in sealed zip-close baggies or store jewelry in a lined jewelry box to limit exposure to air, which can discolor it over time. Exposure to air causes jewelry to tarnish, leaving dark stains on the metal surfaces.
After wearing your jewelry, give each piece of jewelry a quick wipe with a Sunshine cloth or other jewelry cleaning/polishing cloth. (If you wear your jewelry outdoors or in the heat, do a little more thorough wipe-down.) This will remove anything that settled on the surface of your jewelry while it was out of its closed storage, and will really help prevent tarnish from forming. Then store your jewelry in one of the ways recommended above to keep tarnishing elements away from it.
Take off all costume jewelry before entering water, including showers, tubs, swimming spools, spas and saunas, and before washing dishes. Do not wear costume jewelry when swimming in lakes or the ocean. Moisture on costume jewelry often leaves dark water spots that are difficult to remove without damaging the finish of the jewelry.
Put on jewelry after applying perfume and hairspray, as these substances can build up on jewelry and cause discoloration and tarnishing. In addition to dulling the shine of jewelry, the ingredients in perfume and hairspray build up in the crevices of jewelry, trapping dirt and dust. This creates a dark appearance difficult to remove if not cleaned regularly.
Avoid wearing costume jewelry while exercising or during other activities that cause sweating. Sweat discolors some jewelry, especially artificial pearls. The discoloration occurs when the sodium from perspiration dries on the jewelry. Over time, this sodium buildup causes an overall dullness to metal surfaces.