wash with warm tap water, toothpick the reeds and let them air dry. UV light is worse on the reeds than anything else, but a dry place is important too. The fridge is a good place, to store them, but I keep mine in my vest and stored in my coat closet. I get two years out of a call.
I know as a call maker this sounds like a plug to sell calls but it's true. Just remember by nature of material used a diaphragm call is a disposable product and when it wears out replace it. If you don't your calling will suffer and you could develop bad habits from trying to manipulate a stretched or weak call. That said there are a lot of thing already mentioned that will prolong the life of the call.
