If you want to go a step further and separate your tools, you'll need to get a bit more creative. One way is to utilize PVC pipe to make containers for your tools by attaching to two pieces of wood and hanging that from the wall. Another solution is to utilize a pegboard for your larger items as well, as they can hang from hooks similarly to smaller items.
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.