If you are about to place items in storage, you have to find some way to keep the boxes and other small items off of the floor. Larger items can sit on pallets and plastic sheeting, but if you try to stack boxes on those, all you'll do is end up with unwieldy stacks that could fall over. You need shelving for boxes that will allow you to access each box in the stack without having to move too many boxes beforehand. Don't grab just any shelving, though—you need to look for certain options.
Your shelving should be made of plastic or metal—no wood, no cork, nothing that could be easily burrowed into. Good storage facilities do what they can to eliminate pest problems and keep your stuff safe, but in even the best ones, you can get a storage neighbor who brings in some unwelcome guests. Add to this normal regional pest issues, such as spiders or the occasional loose termite flying around looking for a home, and you know you need to find something that will be unpalatable to the pests. You can find inexpensive yet sturdy shelving at home improvement stores and by ordering online.
The shelves you get also need to allow good airflow patterns. Get shelves with relatively large spaces between each individual shelf so that boxes aren't wedged in there, preventing air flow through the shelving unit. Also look for shelves that are grids or composed of rows or supports with space in between, instead of solid swathes of plastic or metal. Those openings will help move air around the bottoms of the boxes, reducing the risk of mildew forming on the boxes.
Finally, any shelving units you get should not extend past your own head's height, if you'll be the one most likely to retrieve things from the storage unit. Items that are too high up will not only be difficult to reach without help, but if you try to get them anyway, you risk the boxes falling on you (e.g., you reach on tiptoe to get a box and manage to slide it quickly off the shelf onto your head because you couldn't get a proper grip on it). Use taller shelving only if the people most likely to get things from the unit are much taller than you, or if you can get a good step ladder to reach properly.
The storage facility manager will also have extra tips on storing your belongings safely. A good storage facility and proper preparation will help keep your belongings in great shape.