Umm.
Well, I’d start by letting him read some Lovercraft, and maybe some Wlater Gibson. (Never too early to introduce them to the classics, and theu’re good jumping-off points to the game!!)
Reagarding the system…
Well, (as written) Cthulhutech offers a pretty graphically violent/depraved universe.
It’s not at all “Civilized” like standard Cthulhu, and some of the scenario seeds in the later books (IIRC), are pretty “torture-porny”.
Also, it’s definitely a “Kitchen Sink” type of setting; you can’t POSSIBLY include everything they refernce in the books into a campaign. There’s war on MULTIPLE fronts, mixed with intense Xenophobia (from without and within) and corruption, intriguie and backdoor dealings EVERYWHERE.
Overall, I also don’t think the rules necessarily work as cohesively as they should, but I guess that’s to be expected when you fuse 2 genres that are somewhat antithetical to each other.
So, I would start by discussing with the GM the themes he wants to focus on and go from there. What does he (and the players) like? And let that guide your campaign setup descriptions. Is he into the “Mecha” side of things? Then I would make that the central plot. Have it be combat-heavy and have the PC’s all be Engel-pilots (or possibly Tagers).
If he’s into the more Cthulhu-esque side of things, they could generate a group of “Occult-Investigator” type of characters.
Be sure to give us updates/session reports. I’m curious to see how “Actual Play” turns out. (I’ve been involved in some one-shots, but not a campaign.)