Customer Database in Excel: How to Set It Up So It Does Not Break

Most customer spreadsheets break because of three habits: two customers on one row, the same status typed several ways, and the same person entered twice. Four rules keep the sheet usable, based on Microsoft's Excel documentation and the FTC guide for businesses: one row per customer, drop-down lists through Data Validation, removing duplicates only on a copy, and treating the file as personal data.