I'm gonna go ahead and be the asshole here, because while it's super great to include--especially meaningfully--people outside your friends, the best advice I can give you is:
Run shit for your friends.
At least at first. Fuck other people. Your friends will understand if you fuck up, don't know a rule, have to go clean up after the dog, whatever. Basically every stressful situation I've ever had as an ST has been because of people I don't fucking know, or that I don't get along with in the first place, but was in the unenviable position of having to ST for, for X or Y reason.
I'm not saying NEVER run for people you don't know. Just... get comfortable with the people you do first, then dip your toe further out. And if people judge you as exclusionary and a jerk for it, they can go sit and spin on their lack of plot, because chances are they don't get any scenes because they act like entitled monkey farts.
Good luck!
P.S. Also, all that stuff @Faceless and @Gilette said. Keeping in mind, of course, the above.