It is extremely important to treat your jewelry with care.  It is never advisable to wear your jewelry while swimming, cleaning, bathing, or while wearing lotions, perfumes, or oils.  Chemical reactions can happen with metals, so it's best if you wipe your jewelry with a polishing cloth after each wear and store it in a small baggie or the box it came in.  If your piece has tarnished, simply use a polishing cloth to clean it right off.  If the tarnish is a bit stubborn, combine warm water with a bit of liquid dishwashing soap (Dawn is great brand).  Use a soft toothbrush to gently brush your piece.