Keep it off the slab
Concrete wicks and holds moisture. Racking or dunnage keeps the flange dry and stops the bottom of a reel staining and softening.
Control humidity
Condensation on a cold reel in a humid building is the indoor equivalent of rain. Ventilation and steady temperature do more than any covering.
Stack safely
Reels can be stacked upright in cradles, never flat on top of each other. Flat stacking crushes the lower reel's flange and deforms the cable.
Label the location
A reel that cannot be found is a reel that gets re-ordered. A simple location code on the tag pays for itself the first time someone avoids buying new cable.