Uncoated sterling silver jewelry is traditionally prone to tarnishing. Basic silver polish can help remove the tarnish and add a soft, aged patina to the piece. If you would prefer to keep your item looking super shiny, you can use a silver dip made for this purpose (Tarn-X) is one brand that is available. These products are extremely hazardous to use and must be used very carefully in order to prevent harm to yourself. Silver polishing cloths are available that have a soft, microfiber surface and an anti-tarnish agent built in (usually zinc). This will give a nice, safe, dry polish to any piece.
Coated sterling silver is another story, altogether. Because of the clear coating that prevents tarnish, you should never buff the piece with a silver cloth, use silver polish, or use a silver dip product. All of these can damage the clear coating that prevents tarnishing. The longer that the piece is protected, the more lovely the luster. Gently wipe these items clean with a very soft, cotton cloth. A clean piece of an retired t-shirt works well. If a piece has an obviously damaged or hazy coating, check with a local silversmith or jewelry store to see if re-coating the piece might be feasible.
Silver costume jewelry is usually made of plastic and should be handled gently and wiped clean with a soft, cotton cloth.
High Fashion silver jewelry is actually coated heavily with precious silver on the outside. If not tarnished, gently wipe clean with a soft, cotton cloth or a microfiber cloth (similar to what you would clean eyeglasses with--no chemicals added). Because of the clear coatings on this type of jewelry, it is best not to try and handle this at home. Check to see if the manufacturer offers a guarantee or warranty on this type of jewelry. The better companies will.
By carefully caring for your jewelry pieces, they will sparkle and enhance your wardrobe. Happy Bling!