If this is a long-term storage solution, place sturdy shelves along one wall of the unit, If not, stack your boxes with these guidelines in mind:
*Stack from back to front in order of need. The boxes that you will access most frequently should be the last ones packed inside the storage unit and be near the door or on shelves with labels facing out.
*Put larger, heavier boxes down first, and then you can stack lighter ones on top. Be careful how high you stack. If boxes are stacked above you head, the whole stack is susceptible to falling, creating a hazard for you and anything breakable in the storage unit.
*Consider using a brick-wall pattern when stacking same-size boxes. It’ll seem somewhat inefficient, since you’ll have spaces on the ends of your stack, but brick wall pattern allows you to remove and replace boxes without moving the boxes above it.