Sterling silver pieces
When you aren't wearing your sterling jewelry, store in a dry place. When silver is being unworn, it can tarnish, but don't worry, that can easily be cleaned. Store it away from wool - will also cause quicker tarnishing.
Silver can be cleaned with a polishing cloth, or silver cleaner.
If you swim with silver in pools or ocean it will oxidize. If you forget to take it off, if you don't clean it, it will eventually brighten back up. If you are OCD, use a silver cleaner.
It is fine to shower and sleep with your sterling jewelry.
14/20 Gold filled pieces
Gold-filled is a layer of gold wrapped around base metal (Brass). It is nickel free and won't turn your finger green. It also doesn't tarnish like silver does, and will stay gold for a long time with proper care (see below). Gold filled is like champagne taste on a beer budget. :)
When not wearing your gold filled jewelry, it is best to store it in a dry place - don't keep it in your bathroom - the constant humidity isn't great for it. This will increase the longevity of the piece.
It is fine to shower and sleep with your gold filled jewelry.
Hey fancy lady! You barely need to do any thing to keep your gold piece looking tip top, cuz you fancy. Diamond rings and other rings with gemstones that are open in the back sometimes need the crud cleaned out to keep them bright and crud free. A soft brizzled tooth brush works well for this, and soap and water. You can use a jewelry cleaner if you prefer.