How do I verify and correct authentication issues that might lead to a 403 Forbidden response in Postman?

To verify authentication in Postman, first check the 'Authorization' tab in your request. Ensure you've selected the correct type (e.g., Bearer Token, Basic Auth, OAuth 2.0) and provided accurate credentials (token, username/password). Common mistakes include expired tokens, incorrect token format, or using the wrong authentication scheme. Always double-check the API documentation for the exact authentication method and parameters required, and ensure any tokens are current and valid.