To find and highlight blank cells or those containing only spaces, 'Conditional Formatting' offers a practical solution. For blank cells, apply a rule with the custom formula =ISBLANK(A1) over the desired range, adjusting the cell reference as needed. For cells with spaces, use =TRIM(A1)="", which will highlight cells where removing spaces results in an empty string. This method helps visually identify such cells for further action or review.