Thinking backwards should push you to avoid the mistake of bringing your belongings to the unit in any order whatsoever. Each item you bring to the unit should be brought with an aim in mind: does the load require a heavy or light item next? Large or small? Does it need something to fill a small gap, or are you starting a new row and require an item to serve as base for more items on top?

Asking yourself what the load requires every time you bring an item to the unit will ensure the unit is loaded in a way that maximizes the use of space and keeps your items safe from damage.