I uncoil the glass and keep it standing in carpet tubes.
I keep the lams taped together like Mitch does, and stored in boxes to keep the dust off.
They should not be finish ground until they're adequately dry, and if they are, then ground, then kept in that same dry atmoshphere, they won't warp... at least not enough to worry about.
I like to keep my lams in board form, or 'rough sawn' to about 3/16 - 1/4" until I'm ready to make the bow, then grind them a day or two before, when possible.