Best practices for conducting internal audits under ISO 9001:2015 include:

1. **Planning the Audit Schedule**: Ensure audits are scheduled regularly and cover all relevant areas of the Quality Management System (QMS).

2. **Planning the Process Audit**: Prepare a checklist based on ISO 9001:2015 requirements and the organization's processes. Define what you want to ask, check, and see.

3. **Conducting the Audit**: Gather evidence through interviews, document reviews, and observations to determine if the QMS is effectively implemented and maintained.

4. **Reporting on the Audit**: Report findings to relevant managers, highlighting both minor and major nonconformities.

5. **Follow-up on Issues or Improvements Found**: Ensure corrective actions are taken and verify their effectiveness.

Addressing non-conformities involves:

1. **Control and Correct the Nonconformity**: Take immediate action to deal with the consequences of the nonconformity.

2. **Evaluate the Need to Eliminate Causes**: Determine the root cause to prevent recurrence.

3. **Implement Corrective Actions**: Take steps to eliminate the cause of the nonconformity.

4. **Review Effectiveness**: Check if corrective actions have effectively resolved the issue.

5. **Update Documentation**: Make necessary changes to procedures and records to reflect improvements.