Attributes
Make product attributes work like real data instead of loose text.
Fixed field names
Use one meaning per attribute and avoid synonymous fields with different names.
Normalized values
Write colors, materials and technical values consistently.
Data type
Save numbers as number and unit where possible separately.
Filterability
Not every attribute has to be a facet; choose use and distinctiveness.
Searchability
Highlight which fields support matching and which are for presentation only.