Hi SJE.
You seem to have the same problem I had before I started playing AW - I was thinking too hard about the game, essentially playing it out in my head before actual play.
Don't sweat it. Follow the rules as written. During the first session, when someone opens their mind to the psychic maelstrom, you'll have a short dialogue. You'll ask him what it looks like, how he does it, what sort of stuff the Maelstrom usually says, and how. They might answer some of this with "dunno, you tell me", which is also fine.
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For example, during my first campaign, the battlebabe wanted to open his mind. So I asked, "ok, what does it look like?"
-Well, my eyes are rolling in their sockets and they're all white.
-And you're shaking uncontrollably and frothing at the mouth, right? [I try to put my bloody fingerprint on it, but it's ultimately up to the player to accept this]
-Yeah, of course I am.
-And does anyone freaks out when you do it in public? [I'm looking for where they're weak]
-Nah, they're used to it. I'm a freaky guy. [Found it! :)]
-Okay, you've got 7-9, that means a vague hint. Do you say it out loud or does it echo in your mind? [again, looking for where they're weak]
-I gurgle and mumble, but I don't say anything aloud.
-And remind me again, are you trying to get information on anything specific, or just generally useful stuff?
-I basically want to know if it's safe to leave the hold.
If this wasn't the first session, I would've consulted my fronts. Since I'm not allowed to have any prep for the first session, I use this opportunity to reveal off-screen badness.
-As you let the Maelstrom rage inside your brain, you lose control over your body. You hear over and over the words "Junkyard", "Massacre" and "Madness". Obviously, something very wrong is going over at the Junkyard.
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Each character can have its own way of opening her brain. In my current campaign, the Driver looks for funny shapes in the clouds or listens to the static on the car radio; the Chopper lights a cigarette and gazes at the smoke; the Gunlugger paints with his own blood and talks to his dead uncle.
Based on these answers and your interaction with the player, you can start thinking about the maelstrom. In my first campaign, because of that dialogue, the maelstrom was a physical phenomenon, essentially a sentient swarm of nanobots. In my current game, it's more of a spiritual thing; maybe it's the Spirit World, or some such. I don't like determining what it is in advance, but I don't hold out details about it when I'm asked. Usually, I just turn the questions back at the players: "Is it possible to lobotomize your third eye and cut yourself off from the maelstrom? I don't know. Do you know which part of the brain interacts with the maelstrom? Do you have the workspace, the know-how, the equipment and a willing or properly-subdued subject? Let's have a look at the workspace rules and see what's appropriate".