How do you approach a code review (as reviewer)?

Understand the intent first: ticket, description, tests. Run it if useful.
Priorities: correctness and edge cases, security, data/migration risk, design and readability, tests, performance, then style (automate style with linters/formatters).
Be specific and kind: ask questions, explain the why, suggest alternatives, mark small things as 'nit' (optional).
Keep PRs small; review promptly.
Approve when it improves the codebase, even if you would have written it differently.