At my high school the rule was that nobody was allowed in the booth unless they were working. Actors/performers only if they were recording something with the sound tech. Anyone who had nothing to do with the show was strictly just not allowed in the booth.
How to go about kicking them out? Well, since my TD made the rule that nobody was allowed up there whenever someone not allowed would come in I would simply tell them that they weren't allowed and they needed to leave. One of the technicians at my old high school who thought she was the reason the sun rose in the morning brought her girlfriend into the booth and got really bent out of shape with me when I insisted that she leave. They finally left though, complaining loudly that I was mean and whatnot. Whatever, those are the rules that I'm given and those are the rules that I follow.
Our
stage manager for Pajama Game let a reporter up into the booth so she could write an article. There was also talk of letting this girl on
headset. I kindly told miss reporter that there was absolutely no way she could be on
headset and not any way that she could be in the booth either. I mean, how was she going to write anything down if there was no light for her to see. The
stage manager thought it appropriate to override me by saying, "I'm the
stage manager and I'm the boss, she's coming into the booth." So down I go to the TD who rages at her and makes the reporter leave. More complaining about me being rigid and mean. Whatever, deal with it.
If you have a problem with people coming into your booth just to hang out, put a sign outside the door that says something along the lines of, "unless your job is a booth job, turn back now." If people decide to come in anyways without purpose tell them to leave. We had a big problem with having all the techs in the booth, that should only have 5-6 people max, coming in before a show. It got to the
point where I couldn't even focus on the tasks at
hand and I made everyone leave and we put up a sign.
Make guidelines about who should/should not be in the booth. Share these guidelines with your crew and then stick to them.