01
Start with stable identity fields
Use separate columns for player, year, brand, set, card number, parallel, serial number, sport, and team. Combined descriptions are readable but difficult to filter or import.
02
Keep numbers numeric
Store cost, estimated value, sale price, fees, and shipping as plain numbers. Put currency symbols in formatting rather than inside the cell value.
03
Standardize controlled values
Choose consistent values for status, condition, grading company, and yes-or-no fields. Small spelling variations create duplicate groups and unreliable filters.
04
Back up and migrate
Keep dated copies before large edits. When the spreadsheet becomes difficult to maintain, clean the columns, save a CSV, and use CardCat's import guidance to move into a visual catalog.
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