fatterSurfer

Good question, but unfortunately hard to answer. Some general advice I guess:

• Listen to directions and act as calmly as you can.
• Remember that they're people too.
• If you're injured, don't underplay or overplay what's wrong with you (this can be hard).
• For that matter, in healthcare in general, just be honest. We're not (supposed to be, not every egg basket is fresh) in the business of judging you. I got into healthcare because I wanted to make a difference in peoples' lives, not just their pulse or breathing. You don't do that kind of stuff if you're going to be a dick about whatever moderately embarrassing but we've probably seen worse thing is happening to you.
• If you're a bystander, unless someone explicitly asks for help, it's probably better to err on the side of keeping out of the way -- or, better yet, go track down some water bottles or snacks and offer them to command staff to give out.

In my experience:

• As a victim, you're explained your injuries, and what symptoms to present when the responders show up. This is really very important. Beyond that, you don't get much of a script. Although there are occasionally exceptions to that, such as "we want you to act belligerent enough that a LEO needs to restrain you" or "about ten minutes in (when LEOs were staging for entry), run/limp your way outside and collapse.
• As a responder, you know (ideally) literally nothing except that it's a drill, which radio channels are reserved for the drill, etc. Dispatch is sometimes in on it to help facilitate.
• As the perp, I had a handler and a general loose flow of events to follow, but otherwise was on my own. So, for example, the 90+ minutes I spent on the phone with a regional FBI hostage negotiator was all me, as was me "negotiating" for lunch when the drill ran over time because we held for a real call.

Hi Literally, I'm Dad.

Heh. No, like most beards, it started out of laziness and eventually started to grow on me.

Yeah, "this can be hard" is a bit of an understatement" on my part