Use new, corrugated cardboard boxes.
Not all boxes are created equal. Use sturdy, rigid boxes.
Check the box certificate
Confirm that the weight and burst strength specifications meet your needs. Check the bottom of the box for this stamp.
Wrap each item individually
This prevents them from impacting while in transit.
Cushion around all sides
Use at least 2" of cushioning material around and between each item.
Seal it well!
Use 3 or more strips of strong shipping tape to close each flap. Don't use 'Scotch' or masking tapes.
Take a picture!
Photos are very helpful in loss or damage investigations.