Built-in rules
Highlight Cells Rules covers greater than, between, duplicate values, text contains and dates occurring. Top/Bottom Rules covers top 10, above average and similar.
Data bars, colour scales and icon sets encode magnitude directly in the cell — often more readable than a separate chart for a column of numbers.
Formula-based rules
The powerful option is Use a formula to determine which cells to format.
To highlight an entire row where column C exceeds 1000: select A2:F100, then use =$C2>1000.
The key is the mixed reference. $C locks the column so every cell in the row tests the same column; the relative row lets the rule move down. Getting this wrong is the usual reason a row-highlight rule misbehaves.
Rule order
Manage Rules lists rules in precedence order — first match wins for conflicting properties. Reorder with the arrows.
Stop If True halts evaluation when a rule matches, which is how you prevent a later rule overriding an earlier one.
Keeping it usable
Applying rules to entire columns (A:A) bloats the file and slows recalculation. Scope them to the actual data range, or apply them to a Table so the range grows automatically.
Check rules after copy-paste — Excel fragments ranges into dozens of near-identical rules over time. Periodically clear and reapply.