Everything depends on what you are looking for.
Going through all questions and references, I will try to give some information.
1st, 2nd and 3rd party audits :
- First party is an audit where only one company is involved. It's also called internal audit. This remains the cases even if you ask some consultant to do the audit on your behalf.
- Second party is an audit where two companies are involved. It's mainly suppliers audits : The client send an auditor to the client. As said for first party, the auditor can still be some independant consultant working on behalf.
- Thrid party is... you guessed it. There are different explainations here, I still don't know which one is the original one : Company - certification body (DB) - standard editor (like BRC) / Company - CB - Accrediation body / Company - CB - client that will have the certificate. In fact, we don't care that much, it's the certification audit.
All those audits can be performed the same way, with the same techniques or methods.
As for lots of things in food safety, I personally don't care how everyone names them if we understand each other.
An audit as a goal (checking if "this" works properly, not having no non-conformance...). If the goal is achieved, whatever the techniques used, then the audit is fine in my opinion.
"Techniques" are quite simple, but don't tell you that much : read the documents, check the records, observe and ask. Don't judge, don't imagine, record facts.
For the questions, they talk about open, closed, oriented, investigation and clarification questions. But the most important thing is : don't give the answer in your question, like "Do you do like this and this ?"
Besides the whole checklists, taking several days to fill in, I currently have 22 internal audit check-list, each one checking in detail a single PRP or system (pest management, cleaning, personal hygiene, HACCP studies,...) This are some of the techniques/methods used in those audits :
- Take the plan (pest control, flows, water taps,...) on site and check if everything is as the plan says.
- Take the list of raw materials and check the specs for each one, the date of each spec, the certificate and its validity of the supplier
- Take the list of raw materials and check on site if there no "registered" raw material
- Take the procedures on site and check if everything is running following document
But the most important thing, in my opinion, is to have (for an internal audit) an experienced auditor, well trained, and even more important able, when (s)he sees a small thing, to think to the possible origins and the possible consequences. So, from the small thing, he will find the main gap in the document or the way of doing things, and help to correctly fill the gap.
Why did I say for internal audit, and not for the others ? Because it's important for an internal auditor to find everything, so second and third party auditor won't find anything, and you won't have any problem with your clients or to get your certificate.