When you’ve finished wearing your jewellery, it’s a good idea to dry with a soft cloth before storing it. Keep it somewhere dry, as moisture can be detrimental. Storing in a dark place is advisable, and some people like to keep a piece of chalk in the box to help absorb moisture.
Another trick you could try is to store the jewellery in an airtight plastic bag, something like a Ziploc bag. But do make sure both the jewellery and bag are dry (or you will be trapping moisture in with your jewellery, and you don’t want that!) and then squeeze all of the air out before sealing. If you want to try this, I would also suggest wrapping the jewellery first in a soft cloth before sealing it up in the bag.