The best preparation will be your internal audits; they will give everybody an understanding of how an audit is conducted. However, there are several issues that external auditors typically hone in on; one of them is document control. Preparing for the certification audit should, therefore, always include a review of all work areas to ensure that there are no uncontrolled documents, including sticky notes.
If you are using one of our certification solutions, you will be well prepared for the certification audit; we will, for example, address typical auditor questions.
Another effective yet inexpensive preparation tool is our video course, How To Deal With External Auditors; it's available in both DVD and Network/LMS versions.