I've been asked to address how I store my paint pallets.
I cut most of my palettes from 6mm float glass, and safety the edges. My palettes are all cut to fit inside lock and seal plastic Tupperware-style containers. I attach feet to the corners and write onto the back of each one what it contains (the name of the paint(s), the liquid it's been mixed with, and whether it has gum Arabic or not). Writing it on the back ensures the writing doesn't get removed as you mix the paint.
Once I'm done painting, I'll gather the paint together into a neat lump on the palette, then surround it with four strips of wet cellulose sponge. I group my palettes together by colour and by temperature of the paint. I stack them on the lid of the Tupperware container, lower the 'bottom' of the Tupperware over the top, and seal it shut. I write the name of the grouping on the outside, and add it to my ever-growing stack of palettes.
Labelling each palette ensures I know exactly what it is, even after months and years have elapsed. Surrounding the lump of paint with wet sponges , stacking the palettes and storing them in lock and seal type containers ensures the paint stays damp -- and clean. I've returned palettes after months have elapsed, and the paint was still damp and required very little mixing to resume working with it.