Cut a couple of lemons in half and place them in a glass container with water. Put it in the microwave, heat it until the water boils, and leave it like that for a minute. The dirt on the inside should then be very easy to wipe off.
Take a large container and cover it with tin foil. Fill it with hot water and add half a cup of salt and half a cup of baking soda. Leave silver items to soak in this mixture for 30 minutes, then rinse them and wipe dry with a soft cloth. All the dark stains will disappear.