I use tiny plastic ziploc baggies (from the bead store) but some use paper envelopes. No need to refrigerate them. Keep them in an airtight canister in a cool, dry place. I put a thin layer of dessicant (that powder you buy in a box to dry flowers with.) Mine last for years that way. One exception is peas and beans which shouldn't be sealed. I've heard they need to breathe, but don't quote me on that one. I keep them loosely bagged and they do fine.

When sending seed, I wrap the baggie in bubble wrap first.

Susan:
Thanks for the information, it is very useful.Viv