Start with a number, not a perfect spreadsheet.
Your inventory only needs to answer two questions: what is in the box, and where is the box? Begin with a numbered label and a short list on paper or in a note you can access from your phone. Keep the list outside the storage unit.
Give each box an identity.
Label at least two sides with the same box number. Add the destination room or category, followed by a few specific contents. “Kitchen — utensils and measuring cups” is more useful than “miscellaneous.” Avoid placing sensitive information on the outside of a box.
Photograph before you close.
A quick picture of the top layer can jog your memory later. Keep it alongside the box number in your own records. For more valuable belongings, retain the documentation your insurer asks for and discuss coverage with the relevant provider.
Make a small map.
Note which groups sit at the front, middle and back. You do not need a detailed floor plan; a simple sketch and a list of box numbers is enough. Keep the next things you will need close to the entrance and leave a clear way through.
Update when things move.
Cross off an item when you collect it and note new additions. Review the list before buying a replacement for something you may already own. An inventory works because it stays simple enough to keep using.

