I get this question a lot so I thought I would share with you what I know about silver and how I clean it. I would love to hear your comments if you use something else that works.
All Sterling Silver is made up of 92.5% silver, the other 7.5% is made up of copper. Fine Silver is made up of 99% silver and 1% copper. Copper is added to silver to give it durability. The copper content is what causes silver to tarnish.
Over time silver with interact with natural sulfides in the air and start to tarnish. It will tarnish quicker in areas with high humidity levels.
Copper, Nickel, and Brass jewelry will tarnish much faster than silver.
To clean your jewelry start by cleaning it with warm soapy water to take off any grime (you can use a very soft toothbrush and gently brush the piece with soapy water; some customers have found that using a white toothpaste works well also). Rinse and dry the piece and then buff it with a soft polishing cloth. I recommend Sunshine polishing cloths. If you use toothpaste make sure it is plain white toothpaste and not any type of gel toothpaste.
There are lots of other ways to clean jewelry, but because most of my pieces are oxidised (antiqued...letters are blackened) I find that the oxidising.