Storing Unused Clay
I know that in the early days it seems almost impossible that you'll have any left over clay from those "tiny little packets", but just in case you do here's a few suggestions for keeping your clay from drying out....
NB - If you use different types of clay with different shrinkage or drying rates e.g. Original PMC / PMC+ or ACS650 / ACS650 slow dry it's best to have a seperate labelled container for each
For short term storage -
Use the outer foil pack that your clay came in..
Make sure your clay is moist (if not dampen it) then wrap in cling film before putting back into the ziplock packet.
Wet a piece of kitchen towel & put into packet with the clingfilm wrapped clay.
Ziplock the top shut. (This has kept clay good for days for me & if you keep check the moisture level daily there's no reason it couldn't be longer).
For Regular Storage -
A home made option is to get a small airtight container (little lidded pots)and put a piece of wet sponge in the bottom (dense make up sponge type).
The moist wrapped clay then goes into the pot and you keep the sponge moist.
This way you can have multiple pieces.
Longer Term Storage -
If you want a good pre-made solution or have larger quantities of clay to store regularly then an American site http://www.pmcsupply.com/ has something called Clay Vaults and Clay Keepers. They are "zip lock" plastic containers with hydrated water crystals inside & they're very good.