A.M.
You just need to save the sheets that they come on and re-apply them there when you take them down. If you're talking about the "jelly" clings, do not put them in a ziploc bag. The different colors will bleed together and you will end up with a blotchy mess by next year (I'm in charge of decorating my hospital unit and someone "helped out" last year by taking down all the Easter jelly clings and putting them in one big ziploc bag. They were destroyed.) Just save the clear plastic sheets they come on and put them back there when you're done. If they are dusty or covered in cat hair (again from experience!) simply rinse them in soapy water and the stickiness will return.