We recommend using a silver cream or anti-tarnish polish to remove oxidation from silver.
The brand that we have found to be one of the best is Wright's.
To clean silver with Wright's;
1) Wet Jewelry with warm water
2) Apply cream with provided sponge, removing tarnish
3) Once tarnish is removed, rinse silver with warm water
4) Dry with soft cloth or towel
Wright's can be found at your local grocery, hardware store,
Village Silversmith, or by clicking on the link below.