The BEST way for an organization to ensure that incident response teams are properly prepared is by conducting tabletop exercises appropriate for the organization.
Tabletop exercises are an effective way to test and validate an organization's incident response plan (IRP) and the readiness of the incident response team. These exercises simulate different scenarios in a controlled environment and allow the team to practice their response procedures, identify gaps, and make improvements to the plan. By conducting regular tabletop exercises, the incident response team can stay current with changes in the threat landscape and ensure that they are prepared to respond to incidents effectively.
According to the Certified Information Security Manager (CISM) Study Manual, "Tabletop exercises are a valuable tool for testing and validating the effectiveness of the IRP and the readiness of the incident response team. These exercises simulate different scenarios in a controlled environment and allow the team to practice their response procedures, identify gaps, and make improvements to the plan." While providing training from third-party forensics firms, obtaining industry certifications, and documenting multiple scenarios for the organization and response steps can all be useful in preparing incident response teams, they are not as effective as conducting tabletop exercises appropriate for the organization.
Reference:
Certified Information Security Manager (CISM) Study Manual, 15th Edition, Page 324.