The intent of ISO 9001 is to encourage the adoption of the process approach to manage an organization. As a result, internal audits (of your management systems) need to adopt a similar approach.
An activity that uses resources to transform inputs to outputs can be considered a process. The output from one process may become the input to the next process. To function well, organizations must identify and manage numerous interacting processes.
The Process Approach involves the systematic identification and management of these process interactions within an organization.
For effective audits, you have to understand the process nature of the system and follow the appropriate audit trails.
For example, auditing to the requirements for quality objectives requires considering clause 5.4.1, ‘quality objectives’, in addition to, related clauses that refer to quality objectives, such as 5.6.1 Management Review and 8.5.1 Continual Improvement.
Therefore, to see if quality objectives have been planned, implemented, monitored, and improved, an audit will need to consider requirements from multiple clauses.
The full BSI 9001 Auditing Tips PDF brochure can be downloaded here: BSI Brochure