Place your copper jewelry in a glass, or plastic container, not metal. I use a drinking glass. Pour enough vinegar over it to completely cover it. Let stand for 5-10 minutes. Rinse. Dry. You're done!
Follow directions used above for vinegar.
This is my least favorite, as it is a little messy, but it will certainly do in a pinch! Simply rub your piece of copper jewelry with ketchup on a cloth until it is shiney. Rinse. Dry. You're done!
NOTE: If you buy a piece of copper jewelry that has a protective lacquer on it, do not try to clean it by any of these methods. Be especially careful if you have purchased a vintage piece as you could possibly decrease its value. A lot of collectors sell pieces that have not been cleaned by them and leave the cleaning up to the buyer if they so desire.