Original foam cradles are great, but not always available.
I recently received some auction items. Individual cars were separately wrapped in brown paper, then wrapped in bubble wrap, then surrounded by styrofoam peanuts inside a sturdy box, which did the job. For items with fragile details, adding a smaller box within the main box should be sufficient.
IMO, the keys are to pack items so that they're snug but not compressed, separated from each other, can't move around within the box, with some cushion around the exterior. Make it so that it can be dropped from chest height.