Utilized Pegboards - Pegboards are a great tool that can be used almost anywhere in the home for organization. The same is true for your shed. For small tools, such as hand shovels and rakes, attach a pegboard to a wall and use various hooks and hangers to place hand tools and other items on. This gets them off the ground, out of the way and in a consistent spot that is easy to find.
Site Preparation for Storage Units - 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.