Move It Out - When organizing your shed, it's important to consider what you use it for and the climate you live in. Keep in mind, many sheds are there to protect your items from the elements, rarely are they insulated enough to protect against extreme cold or heat. If there is anything currently in your shed, such as paint or liquids, you'll want to move those to a place that is more temperature controlled. Additionally, any pet food or paper is surly asking for a visit from any pests in the area. Move them inside the house where you can ensure their quality.
Before installing storage units, lay down cinder blocks, concrete piers, a concrete slab, or at least crushed stone. But don't stop there. Make sure the supports underlying the floor are made of pressure-treated wood.