On-site hacking requires some acting ability -the ability to act like you have a valid reason for being where you shouldn't be and undertaking questionable activities while there. There's nothing difficult about this - just pretend you own the place.
Strut down the center of hallways holding your head high. Smile and say hello to the people you pass. I learned this trick in school, where we needed hall passes while classes were in session if we wanted to leave the classroom. All throughout junior and senior high, I never got stopped once by a teacher or hall monitor for not being in class, simply because I acted as if I was on some official mission for the principal. (It helped that I was a "good kid.")
So do your best to keep your cool. Have a reasonable story prepared in case you are stopped and questioned, and try to tell it without fumbling for words. Here's a hint to help you do that.
After rehearsing a story in your head for the umpteenth time and finally repeating it aloud to a security guard, the quickness with which words come to your mouth may seem to you to be too well-prepared, too fake to your ears, and you start throwing in "uhhmm"s and "uhhhhh"s to slow yourself down. Don't do that - it sounds really bad and it takes away from your credibility and sincer-ity. Talk at a normal pace. Say your prepared script without worrying if it sounds fake. And throw in some company insider lingo or gibberish to give yourself an extra believability edge.
