Start here. This is the direct spoken answer to practice first.
Why this question matters
A pull request review protects contracts, runtime behavior, and maintainability while sharing context across the team. Compilation is only the first check.
I first understand the intended behavior and keep the review scoped to that change. I check API contracts, validation, authorization, error behavior, data access, and whether the tests prove the important outcomes. I also look for accidental secrets, unsafe configuration, or public compatibility changes. My comments explain the concrete risk and distinguish blockers from suggestions.