Nothing has to be prepared.
A visit is one location, 60 to 90 minutes, with someone who deals with the computers present. If nobody who uses the machines is there, the report explains what we saw without being able to say what it is used for, and that weakens it.
Nothing is changed during the visit. Nothing is installed, no settings are moved, and no accounts are touched. If something is failing while we are there, it is written down for the report and left alone until you say otherwise.
You do not need to prepare anything. You do not need to find passwords, and we will not accept them if you offer. If you have a contract or a bill from whoever set the equipment up, it can be useful, but it is not required.
See What We Look At for the ground the visit covers.