I find it's a good idea to have some sort of discussion about the campaign beforehand. If half the players (as opposed to PCs) are expecting an actionfest and the other half are expecting mostly diplomacy, then there is going to be a problem. The 40k background has a bit of a learning curve and some effort should be made to bring people not familiar with it up to speed, if only so they have some handle on what's going on.
I agree! I am know to run a pretty dynamic action game, more often than not. I'm actually not very good a investigative-type games… GM wise. But still, I try to tell players what the game/campaign's mood should be, according to me at least. Other times it has gone without issue.
Sometimes a guy acting a bit strange can be a laugh. For example we have an absolute bastard of a Raven Guard Techmarine who during a mission booby trapped a dead body with a melta-bomb. He carried the guy around, with the melta bomb inside him, for the rest of the mission, looking for a good place to put him. He didn't find one, so when he got back he spent the requisite xp to turn the guy into a Servitor follower. Fred the Servitor has become the KT's robo-butler and heavy weapons guy, and we all love him.
On the other hand, the same player asked me whether he could persuade the rest of the team to allow him to install melta bombs in the other PCs. I told him that if he did this then he'd face trial from the Inquisition and the Lords Dragon, and faced a high risk of being executed.
Try and think about the in-universe consequences of their actions. That normally works for me.
Agreed on this as well. The off odd action can indeed be great! My group of friends' many year of gaming has always included it (once I had a sniper body surf on top of a rebel PDF along a hallway…unsure why haha), but also it means that no one really takes games seriously… ever. Except a few of us. Also in universe repercussions are the standard for minor things like the UM's actions, I had him killed by the party's favorite NPC/"partner."
As to the Ultramarine who sounded so fond of Chaos, I would probably have created a daemonic creature, inadvertently summoned by the obnoxious marine's actions, stat it to utterly outclass the obnoxious marine, and have it call him out on his honor to one on one combat.
I suppose this means my answer to the OP is that I tend to put in-game consequences for griefers, and steer things in just such a way as to have it work towards that player's character's demise.
If they're serious about playing the game, they'll reroll and hopefully be a little wiser, if they don't reroll, I'd rather not have them at the table anyway.
Also I try to be upfront and honest about how this game is going to be, and I don't sugar coat anything. "We are playing Deathwatch, and the way I run involves a lot of action and very little dialogue with NPCs and problem solving". "We are playing Dark Heresy, in combat, most of the things I bring out will kill you. I fully expect running away to be a big part of this game, so I'll be focusing the game on more investigative and social activities".
He didn't roll again, most of the group played again at different meetings, but he admitted that it was never his setting. The NPC challenged him to an honor duel/execution and lightning attacked him to death with a power sword on the first round… it was a big laugh, even for the UM's player, which was good. Yeah, I told everyone how it was (I was a last minute guest GM for a group I normally didn't go to despite knowing everyone in the group fairly well).