Six lines to write into the brief for a recurring data pull (source, period, fields, what to do when the source changes, output name and a sanity range) so later runs stay comparable with the first.
Five matching rules for merging two lists without double counting: one agreed key, careful normalizing, a rule for conflicts, a review list for near matches and an audit column.
A five-line footer for any recurring report, covering sources, period, changes, owner and review date, so anyone can trace a figure back to where it came from.
How to build a small invented or masked sample with the same shape as your real data, so you can brief a helper without handing over anyone's personal details.
Five quick checks for a spreadsheet someone else built: recompute one total, count the rows, read the units and dates, click into the formulas, and try one edge case.