The best way is to use a silver polishing cloth from a reputable jeweller. I don't believe its possible to polish sterling without removing a thin layer of metal ... I've read that the only metal polish that doesn't work in this way is gold polish because gold is so inert that it doesn't tarnish.

I only use the silver polishing cloths (infrequently) on my sterling jewellery, as well as the sterling tuning pins on my pipes. Avoid dipping it in any tarnish remover or similar product as you have far less control over how much metal is removed than with the cloth.

Mark O - Ohio