It's best to take jewelry off when bathing, exercising, swimming or cleaning. Storing in an airtight container (like a plastic baggie) will prevent accelerated tarnishing.
That being said- Sterling Silver and Brass both tarnish with continuous wear! A warm bath of soapy water and a light scrub with a soft brush will clean it up. A light buff with a polishing cloth will bring back it's luster and shine.
Brass can turn skin green- it's a natural chemical reaction! Keep polished and apply a thin layer of clear nail lacquer to prevent this.
Pearls are very soft and are susceptible to scratching so wear with care. Always apply moisturizer, perfumes, or other cosmetics before you put on your pearls. Wipe with a damp cloth to clean.
Refrain from treating your ring to any extreme temperatures as this will permanently damage your rings ability to change colors. Remember to take it off when washing hands/showering, etc!