When you first walk into any kind of casting, the first thing you will be expected to do is sign in. Even though castings often are running late, you can't count on this, and most people running an audition like to see that you've made a point of at least being punctual, as they'll want you to do the same should you book the job. Keep focusing on what you have chosen to do. That's the most important concern you have as an actor. Not the other actors, not the quality of the dialog, and not even whether or not you get the part.
Actors are a very sociable, insecure bunch.
It's okay to ignore the other actors and work on your sides. You only get one shot at this audition, and if you're distracted or unprepared, you're wasting your time talking to Joe actor. On the other hand, if an actor waiting with me is reading opposite me for another role in the same scene, I like to work with that actor on the lines to help prepare for the audition. Whatever you do, keep your head, focus on what you're there to do and stay relaxed. Don't sabotage yourself.