What to observe
Note whether the leak is isolated or widespread, whether it follows rain, and whether there is an obvious crack or penetration. Those details help separate a localized repair from a larger drainage problem.
Crack-related seepage
If water tracks directly through a visible crack, start with foundation crack repair. If multiple areas seep, broader interior or exterior waterproofing may be needed.
Interior vs. exterior response
Some wall-water problems are managed from inside; others are better addressed from outside. Compare interior vs. exterior waterproofing.