Hi Suhailams,
If you are speaking about Vendor audits, you need to frame a checklist with all the compliance points you need be it Statutory like payment of wages,EPF,ESI,PT,Returns under all acts etc, Process oriented if any like material specs,other audit related also can be included ISO documentations can be Quality,food safety,employee safety etc.
Beyond this as a part of verification process you can obtain a COC (Certificate of Compliance) from the vendor which can ensure that Vendor complies and represents the same every now and then.
As suggested by our friend Shrikanth, audit is a deep subject,unless some one is competent we cannot prepare a checklist easily.