How to clean tarnished silver jewelry:
Wash tarnished item with a mild soap, then place the piece on aluminum foil in the bottom of a pot. Add a baking soda solution of 1/4 cup soda and a few teaspoons of salt into 1 quart (4 cups) boiling water. Cover for a few minutes. Then rinse and let dry thoroughly.
How to clean gold, silver, platinum, diamonds, sapphires & rubies:
Soak in 1 part ammonia to 5 parts hot water (from 10' to 1 day). Scrub front and back (a lot of goo hides inside the item, not outside) with a toothbrush. Make sure to do this over a closed basin so any dislodged stones land in the basin and not down the drain! Rinse and dry.
Sensitive jewelry cleaning - like emeralds, opals, whacky enhanced rainbow topaz, etc:
Use a warm damp cloth to wipe off. Opals can additionally be oiled with mineral oil or the like.
If in doubt, take it to a jeweler! At least once per year (more often as the item ages) take it to your jewelry for a check up. Jewelry is just like a car and needs to be maintained and occasionally rebuilt/reinforced. Keep your jeweler busy & in business- happily wear your jewelry often :o)