Audit sample files are distributed in the <TOMCAT_HOME>/classes/alfresco/extension/audit directory.
Samples can also be downloaded directly from the following location in svn:
http://svn.alfresco.com/repos/alfresco-open-mirror/alfresco/HEAD/root/projects/repository/config/alfresco/extension/audit/
When using a sample file, remove the .sample extension.