The players in my troupe tend to shoot first, shoot second, shoot everybody, and then not bother with the questions. This can make it hard to develop stories sometimes. Anybody have any suggestions on how to slow them down without doing any permanent damage?
This is a recurring problem in most fantasy RPG. It's best summed up as "Kill them all, Speak with Dead after."
Use some pavlovian reinforcement; You can, as a storyguide, penalize their XP awards, and award an extra point or 2 for good roleplaying. Heck, award them M&Ms or something on the spot.
"If dropping Hints doesn't work, start dropping bombs." It's not just US Foreign Policy, you know...
Demonstrate that there are in game repercussions for killing everyone in sight; The Quasitores would definitely take an interest in such behavior. Also, the covenant might find itself politically ostracized for such behavior. As a last, final measure, senior tribunal members might decide the troublemakers are too much, and drop a wizard's war on them. Or worse, they get framed for a serious hermetic matter, because someone went through all the trouble to manufacture convincing evidence that points the finger directly at them. They have a limited amount of time to clear their names, and have the Quasitore mention that any violence in this matter will be a clear indication of guilt.
How about a situation where they can't win?
A situation in itself that absolutely need them to speak/use patience/negociate/follow hint and if they do not they experience dire consequences (you punish them).
A powerfull faiery come to them, lurking around the covenant. The fairy is anoying maybe acting in a potential "menacing way". If they simply go out and blast the creature aways with magic, make it he creature and old merinitae best faiery friend that had came to the covenant on the behalf of the mage. Or better, make the creature an ex-merinitae that as gone trough the becoming and is now a faiery. Bring the Merinitae wrath on the covenant, as suggest above the Quaesitor, the ostracization, etc. etc.
If they are carefull and speak with the creature, lurk them outside the covenant, the promest of power/secret/vis/components/adventure. Hell, make them save the day by learning an important sub plot hook about the creature that will lead them to another thing and another. At each turn keep them on their toes with encounter that can be turned against them if they act harshly without proper consideration.
That would be my first tought...
-Bellysarius
Don't be afraid to kill their grogs. That's what they are there for. Ranged weapons are excellent for that. So is mind control ... unless they thought to extend their Parma, even shield grogs don't have MR. And they're typically within reach of their magus. Wound the magi, they'll lose seasons of study. Be sure to remind them that exertion may cause wounds to worsen. Once that is done, you can make them deal with a situation where the missing characters would have been really useful.
Don't forget personality rolls, reputations and the effects of the Gift. Check out the loyalty rules in Covenants and have their income base start to look for greener pastures (e.g. other Covenants who might be interested to learn about the character's vis sources or other "presents" the player's ex-covenfolk might bring).
While their heavy hitters are rampaging away from the Covenant, have a band of "adventurers" sneak into the "sorcerers's lair" and steal (or destroy) their treasures (money, books, items, random pieces of lab equiment -- the lab must then be restored, which takes time and money). Have the ghosts of the slain haunt their murderers. Have demons take advantage of their penchant for violence. Magnify collateral damage (oops, that "shady character" really was the runaway son of the Duke).
Take them to an Infernal regio: they may have a field day smiting demons (look! Infernally-tainted vis!), but between the spellcasting penalties and the generally unhealthy environment, you shouldn't have much trouble getting them to overextend themselves. Surround them. Besiege them. Make them miss sunset and lay some curses on them while their Parma is down. That's a problem that cannot easily be solved by blasting through stuff.
Play out a session where your own magus leaves on an expedition with some grogs played by the other players and have him spend their lives to achieve his goals ("Go forth and disarm that trap.") If they rebel, well, you now have established precedent to have key grogs refuse to take their orders in the future.
Some funny advices from Amber DRPG.
"You see something moving in the corner of your eye, what do you do?"
=> "I blast it!!!"
=> The old woman falls down, a smell of rotten pig coming from her, and whisper "Why? I just wanted to warn you" before she dies.
Or
Your Pilum wash over a green-skinned giant. He looks at you, and says "Why are you trying to hurt monjo? Dad!!! Some bad people are trying to hurt me!!"
They kill people? Sometimes, they lose precious information. Or these people have powerfull allies who want revenge. And if they have the habit of killing first, summoning ghosts later, it's better: Have a demon impersonnificate the ghost, leading them to corrupted knowledge.
All these murders are sure to drawn heaven and hell attentions, as demons may take a particular interest in their covenant, and a saint may try to redeem them, or teach them humility before the power of God.
Some infernal auras might very well devellop near their covenant, created by the demons drawn to them, and tainting their vis. They may be forced to seek heaven's help, but they may need to attone for their sins first (something like going alone on a pilgrinage with only what they wear and without using magic at all, or doing good works, whatever)
Put them in situations where violence can't solve things.
Say, the church has heard of them and their depredation. The local bishop, being something of an enlightened man, has heard of the OOH, and doesn't know if he must trust the rumors or not. So, he sends someone to investigate on them, see if they truly are evil, or victims of the populace's fears.
If they kill the envoy, they'll bring the church AND the quaesitores on them. But how will the man react when he sees demons roaming the countryside of their covenant, drawn by their sins?
If they devellop a reputation as cold-blooded killers, have everyone desert the countryside. Their covenfolk might flee, to. And soon, they'll be alone and starving.
Have them hire new covenfolks. The only ones they can find. Shaddy folks, who rob them before disapearing.
And what of the quaesitores? If they attract so much attention, they'll be accused of molesting the faeries, consorting with demons... And it will be true! Even if they just go to an infernal aura and blast some demons, they may be accused of drawing hell's attentions to the OOH... Which will also be true 
Nothing may stay hidden, so their murders will be known. And what when those quaesitores find those aforementionned infernal auras? How will they defend against this?
I'm going to be something of a jerk here and ask: is this a problem?
It's not how most of us would play Ars Magica. It's probably not how most of us would play Shadowrun, for that matter. But the players seem to be enjoying it. So the question I have is: are you asking because you don't enjoy this style of game, or because you think your game should be more "cultured" or "refined"?
If you want to steer them to a more conventional Ars Magica, the suggestions provided so far are probably fine; although before you do anything I'd talk to your players and let them know that you're going to start introducing consequences for their actions. Give them a chance to change before you start punishing them... if they're not aware that you're unhappy it's going to seem arbitrary, and you don't want that.
A compromise might be to turn back the clock a bit and set your saga during the height of the "Join or Die" era. The PCs can be helping house Flambeau (you've got Flambeau, right?) wipe out the Ordo Miscellanea. That still encourages a more "wild west" mentality, and the consequences are... that more badguys hunt down your troupe for revenge. They're probably going to consider that a Good Thing (TM) and you get you add verisimilitude to your games without coming off as a badguy yourself.
It's only a problem if people aren't having fun. If you aren't having fun, or if they aren't having fun, then it's a problem. If everyone is having fun, smash more face.
If it's a problem, then you're looking at ways to create fun alternative scenarios. Save Damsels and children, have a tribunal, redcaps, etc. If they kill the Damsels and children and redcaps, talk frankly with them about how you're not sure if this is the game you want to play in.
-M
Sigh, yeah, been there. Maybe not "most", but, depending on the tolerance of the individuals involved, far too many.
Okay, first, some Gaming Theory. (There is no one answer, so any answer will be theoretical- this is my theory. ahem. On gaming. ahem.)
Many of the above suggestions above would be great, but they assume or ignore one or more of the below "truths" (ymmv). Depending on whether those assumptions are correct or not, those suggestions will succeed, or fail miserably.
There are 3 things going on here, as with any game. (And these are broad generalizations- exceptions will exist, but I'd think everyone would agree generally, if not in detail.)
(And I'll use GM instead of SG, because I feel this is true across all RP games.)
- Different people game for different reasons. Accept it, and don't fight it.
Some like puzzles and intrigue, some like violence and comedy. Some tell stories, others vent frustration. Some will only play ego-projections of themselves, others are content assuming the persona of pre-generated characters. Some create heroes and order, some create villains and destruction, but fewer are happy with complex characters with complex motivations and goals. A Game Master who has different reasons to play than her/his Players, or simply has different expectations of them and the game, has a big decision ahead - to tough it out, try to change them, or give up.
Because different styles do not always work well together, one "a-hole" who is not in step with the rest can spoil the fun for everyone else. Doesn't matter whether they are the psychopath who kills when everyone else is trying to be subtle, or the drama-queen (male or female) who grabs the spotlight for long emoting on their familiar and their long-lost love, or the power gamer who solves the entire adventure early with one reality-bending spell, if they don't fit, they don't fit. And the GM has as much right to "fun" as any Player, maybe more.
-
Players tend to learn the "right" way to game from examples. Usually from the first "fun" game they're in, and from there only from what they see as "positive" examples. If a powergamer never sees someone having fun with an intentionally inefficient "concept character", they'll never go there, never even stop to consider it as an option.
-
Players get a feel for a GM (or for their previous/first GM), and how that GM's world works, and if that GM changes styles without warning, or if the Players can't figure out their new GM, they'll still respond as they did previously. If this gets them killed, they often see it as the GM's fault. If a GM is new to a group, or if they change too often, everyone's expectations will become frustrated, and the game is doomed. (If the Players are accustomed to a GM who constantly changes, that will be the constant pattern they adapt to, np.)
Exactly.
So, first, figure out your players, and yourself. Would they enjoy a game where they are NOT "killiing everything"? Do they think the highlight of the session is not "solving the puzzle" or "beating the enemy", but the bloodbath where everyone downrange gets killed dead, Dead, DEAD!!! Does no one of them have a non-combat spell? Well?
If so, do you want to try to change them? (And easier said than done!) Can they play the game you want to play? If so, it probably won't happen in one session, so accept that some compromise will be needed until then...
Excellent, but more, make it clear that violence will only make things worse. (Given half an opportunity, bloodthirsty players will find a reason.) And even "reasonable" Players who game as a release will still need to feed that need at some point, so keep that in mind for "eventually".)
Many players are not used to thinking about "consequences", and many game systems/worlds reinforce this type of thinking. The say "If it's downrange, if it's not us, then kill it! ... and then loot the bodies!" They operate as if acting in a vacuum, with no repurcussions, no social backlash in the world around them. Talk to them 1) about cause and effect in a society with laws and communities, but also 2) if they'd still be happy playing in such a world!
You don't want to hit them with a hammer if they never knew that there was a chance for the hammer - that will only frustrate them. But fair warning, and then the smackdown, that's fair, and a lesson better learned. Talk to them, get everyone on the same page, then reinforce that page with rewards for good behaviour.
And those rewards can include XP! If you give little XP for "killing", but sizeable rewards for "being clever", then they'll all think twice about it. Hopefully. (Or it will become clear that it's a lost cause, and you have a different decision to make.) 
One approach to the problem is the "glass onion" foe. There is no one enemy that is not controlled by someone larger and more sinister above them. The clumsy Thugs are hired by the local Criminal who is part of the Gang who are part of the Guild who are run by The Crime Lord who is paid by the Sherrif who owes his fealty to the Baron who is indebted to the Bishop who is following orders from the Cardinal who is corrupted by the Demon... you get the idea. (You don't even need to figure it all out at first - just the beginning. Let the rest tie in to something that comes up later!)
And each time, the more information they can get, and the less warning they can give the next level up, the better off they are. They learn subtlety, they learn restraint, they learn the penalty of a slash-and-burn approach - right up until they get to destroy something really unpleasant, at one level or another, which is that much more satisfying for the wait, every time it happens. Good for you, good for them.
Some people just don't have the temperament. If they have the potential for it, they may just not know how to enjoy that more "subtle" style of RP'ing. If the latter, it's up to you (and any Players you know who do appreciate that style) to show them the joys of your way.
But remember- there are 101 ways to Role Play, and every one of them is right. Just not right for every one.
There is nothing that says that good players, even good friends, all RP the same way. It's a tough call, but finding folk who do all have the same approach may be the only way to achieve what you're looking for.
As chuck norris said... "kick in your face, hook kick in your face... every action has its consequences" 
Anyway, if I understand correctly, his problem was less than the killing than with the fact it became more and more difficult to introduce stories, as they killed every NPC right on the spot.
Like, a courageaous peasant comes to ask for their help against the Evil Monster (which needs only to be killed, like they do!!!!) who has taken over his village, but they kill him before he has spoken
Flambeau Arch Magus comes calling...Could you please kill this earth elemental that is being a pain...
If they try to frag the Mage, they have a problem... 
He could just kill them...
He could turn them over to tribunal,
then Wizards War them...
If they refuse, he might not be well disposed to them when they need something...maybe help getting out of trouble at the next tribunal.
This is the example of something that they CAN'T reasonably think to kill. If they are THAT 'trigger happy', that they shoot that fast, punish them (shrug)
Of course you should warn them before hand...
Yeah, magi can be like that.
But you know what they say- "A riot is an ugly thing... and once you get one started -- there's little chance of stopping it short of bloodshed." 8)
It's important, for any GM/SG with a pre-conceived story, to have more than "one" way for the PC's to get where they need to go. If there's only 1 clue, or only 1 person, or only 1 spell, or whatever, and that somehow fails...
Be flexible in your hooks. If one peasant is killed, send a small delegation. If they're killed, send their kids, with a priest. If they're killed... have a riot.
If your players are cold bloodidly murdering those who are not a serious threat to them, whether mortal, magical or fae, then make up some house rules for corruption.
Basically if they consciously choose to break the rule 'Though shall not kill' for no good reason, they are allying with the infernal and should be treated as becoming infernally tainted. With all that comes with it, penalties in other auras, detection by the virtue Sense Holy/Unholy etc.
Yes, the theory of the ars magica world is that everyone kills occaisonally, that it is regretable but not exceptional. But an important issue is remorse and seeking to be forgiven for your sins. Normal knights go to church once a week minimum, might go on crusade if they are feeling particularly squitty and would probably retire into a monastery if they survive to old age.
For those who go around sinning without any attempt at making up for it (and I doubt your magi are tithing, attending weekly church etc.) then there should be consequences.
QFT - An infernal aura may very well develop within the Covenant.
This is even worse that what I said previously, but would fit very well 
Of course, I was just oversimplificating and joking a little.
I always found out that, once a game is started, you can play a long time just by using the logical consequences of things, even with trigger-happy players.
On another hand, if they so like to kill, it would probably please them to play Icelandic Wars, followed by a little mongol invasion... The Order at war, in short
So was I... a little. 8)
But that's a good idea- if they're that bloodthirsty, and really, REALLY just want action and violence... have the Quasitores and Flambeau hoplites give them an offer they can't refuse!
"You will move your covenant to the Holy Land/Odenic lands, and fight the good fight... or be tried for crimes against the Order."
Something like that. Just change from a calm, civilized environment to one where action and violence are the expected norm. Once that's done, maybe everyone will be on the same page, and happier?
Sometimes you just have to let players take their licks and suffer for foolish decisions.