When buying silver, check if you see any of the following engraved on the item to make sure that it is real silver: sterling, 925, 92 or 92.5. Although there is no guarantee that it is real silver when you find any of those mentioned engraved on the item, it is always a good option to buy from a reliable source. For more info go to http://www.silverchatter.com/2009/02/how-can-i-tell-if-its-real-silver.html
Genuine sterling silver jewelry (92 ½% pure) will usually say sterling or s/s. Lots of jewelry is just silver-plated. If you see places on you item that are green or peeling, it is probably silver-plated. A nitric acid test can be done to test your jewelry buy placing a small drop on your item. It will turn green if it is not sterling silver.