How can pick up the professional Audit from first scene?

First of all, look for the process flow and understand the critical control points and chance for deviations. Then go for monitoring checklists and SOPs for the relevent process flow.

In my point of view I can say the audit is professional from first look when he/she are organized and follow a specific procedures to follow

looking how work going on is it like what written or not.

checking the system  of work. 

the policy for the organization implemented or not.