I have wrote, in the past, techniques for cleaning sterling silver jewelry. I found a new one I wanted to share. I haven't tried this myself, so I can't tell you how well it works from experience.
The first thing to do is mix together equal parts baking soda and water to form a thick paste. Dab this paste liberally onto your silver-plated jewelry and let sit for an hour.
The next step is to scrub the jewelry gently, using an old toothbrush and the paste. Rinse the paste off completely, and let dry.
Place a sheet of aluminum foil in a shallow plastic or glass bowl. Sprinkle 2 tbsp. of baking soda and a 1/2 teaspoon of salt onto the foil.
Put your silver-plated jewelry on top of the foil. Pour hot water into the bowl, on top of the jewelry.
Cover the bowl and wait 5 minutes. Remove the cover and take out your jewelry. The foil, baking soda and salt (which must be dissolved by the hot water) creates a reaction that removes the tarnish from the silver.
From: eHow Articles