Lots of good advice here, but I have a couple of things to add that might help.
I have a sliding scale hourly rate that depends on how many people. More than 10 and it goes up 50%, more than 20 and not only does the price go way up, they have to pay for an additional manager to be on site.
I’m a bar, so I don’t mind prop bottles, but I tell people that if they don’t want to go overtime (and the price goes up 50% for any additional hour other than those agreed upon), don’t bring an entourage and don’t allow drinking. When I explain how any of these things are likely to drastically increase their costs, they get it. I also provide free water (and if they’re nice, occasionally juice or soda from the gun), and will give them prop “cocktails”, with an additional cleaning charge if they use more than a few.
Laying out these ground rules, in writing, in advance, tends to encourage good behavior. I make it clear from my tone, and the very specific confirmation email, that this is work, not fun. And that there are consequences for forgetting that.
I also ask everyone if they have insurance coverage. Most independents don’t. So I request $500 in cash at the start (or Venmo), and they get it back if all goes okay. My manager does a sweep at the end, and nearly everyone gets their full deposit back.
When I first started booking shoots we made a lot of mistakes, and learned exactly how strict we needed to be. Doesn’t mean we can’t also be nice, but as most of these indie shoots are only semi-professional, they respect firm parameters.
And having a friendly but firm manager on site (if not always in the room - we do point out all the cameras, though!), is essential.