Small copper items can be cleaned by boiling them for an hour or more in a pot containing a mixture of 1 cup vinegar and 1 tbs salt per quart of water. Wash with soap and water, rinse and dry with a lint free towel. Use commercial copper polish on larger items. Just be sure to thoroughly wash the items afterward with soap and water to completely remove all the polish residue. Otherwise, it will leave a green stain.
Slightley tarnished metals can be cleaned with a homemade paste of equal parts of slat, vinegar and flour. Rub it on with a soft cloth, rinse and buff. For stuborn stains, rub the copper with salt and vegar or lemon juice.