I just got back from my first testing engagement, and I'm still trying to organize my notes from everything that I learned. I went with an accomplished tester, and was able to learn many of the tricks of the field. Fortunately, the site we were at was not that big, nor were there many machines and servers to test. I think we had 10 servers to test, and 10% of the 70+ workstations. So, it wasn't that bad. Site physical security was pretty easy to test, as the grounds were relatively pretty small.
However, getting on the base was pretty interesting. When driving on, contractors were supposed to stay to the right and go through a special checkpoint. We missed that. We ended up in the regular truck checkpoint. We were greeted by an 'older' gentleman who asked to see our IDs. Upon showing them, he asked where we were going. He seemed entirely put out by the fact that we would have to turn around and go through the regular contractor checkpoint. So, he "cleared" us right there, and called ahead to the booth and told them we were clear. We drove up, they gave us our pass, and we drove off.
The next day, we followed the proper procedure.