Wood furniture will be well served by a good wax polish before it goes into storage.
Surround chair and table legs - the parts that bulge and are likely to get scratched - with a piece of cardboard. You can use tape to fasten the cardboard pieces together, but do not use tape on the wooden parts of furniture.
Put your largest pieces into the storage unit first.
You can sometimes stack a couch on its end, so it takes up less space. If it has a curved arm, you can put a small trunk or other short item under the arm, so that the full weight of the couch will not rest on the arm.
Protect mattresses and box springs with plastic covers, available in all sizes at the storage locations.
Stand them upright and store mirrors and framed paintings between them.
Always stack heavier pieces on the bottom, lighter pieces on top.
Protect furniture from dust and scratches. Moving blankets or regular blankets work well. Bed sheets are a good choice for dust covers. Do not use plastic sheets over wood furniture.
If you will need access to your stored items, leave an aisle so you can get to the back of the storage room. Or be sure what you need to access is in the front of the room, closest to the door.