I'm running my first campaign, which I'm really enjoying and I'd like the opinions of more experienced DM's out there

My question is about combat and how/who an NPC chooses to attack. 
This isn't about simple NPC's such as beast and monsters, or either a bbeg, but rather the NPC's that fall in-between that. 

Obviously I know the strengths and weakness of the party, but I don't want to target people specifically because I know who's the 'strongest' or 'weakest' or choose randomly.
I'd like for there to be some thought behind the decision, this is what I enjoy doing as a DM.

I can use an insight check or general intelligence check, but I wonder if anyone else does it differently?

I would be great to hear your opinions

Quote from Rossi91 >>

I'm running my first campaign, which I'm really enjoying and I'd like the opinions of more experienced DM's out there

My question is about combat and how/who an NPC chooses to attack. 
This isn't about simple NPC's such as beast and monsters, or either a bbeg, but rather the NPC's that fall in-between that. 

Obviously I know the strengths and weakness of the party, but I don't want to target people specifically because I know who's the 'strongest' or 'weakest' or choose randomly.
I'd like for there to be some thought behind the decision, this is what I enjoy doing as a DM.

I can use an insight check or general intelligence check, but I wonder if anyone else does it differently?

I would be great to hear your opinions

 I can very easily slip my thought process into different characters, so I go off of "What does this NPC think is the bigger target based on what THEY know or see. What have they heard? Did they know the players are coming? did they get any info?" that kind of thing.

Except for Beholders. Metagame the HELL out of your players if you're playing a Beholder.

Quote from DevanAvalon >>

Quote from Rossi91 >

 I can very easily slip my thought process into different characters, so I go off of "What does this NPC think is the bigger target based on what THEY know or see. What have they heard? Did they know the players are coming? did they get any info?" that kind of thing.

Except for Beholders. Metagame the HELL out of your players if you're playing a Beholder.

I do the same. But I like to add Illithids to your metagame list - my flayers are mean buggers :-)

Quote from Funkbas >>

Quote from DevanAvalon >>

Quote from Rossi91 >

 I can very easily slip my thought process into different characters, so I go off of "What does this NPC think is the bigger target based on what THEY know or see. What have they heard? Did they know the players are coming? did they get any info?" that kind of thing.

Except for Beholders. Metagame the HELL out of your players if you're playing a Beholder.

 

I do the same. But I like to add Illithids to your metagame list - my flayers are mean buggers :-)

Mind Flayers only can be metagamed if they've gleaned into the players' minds though! ...like say, from a previous encounter or straying too close to the Elder Brain...

Thanks for your advice, especially when to metagame for certain monsters, I'll keep that in mind!

Most of the time the enemies have little to no idea who the party is, were playing Curse of Strahd so it can be quite cut throat

Quote from DevanAvalon >>

Quote from Funkbas >>

Quote from DevanAvalon >>

Quote from Rossi91 >

 I can very easily slip my thought process into different characters, so I go off of "What does this NPC think is the bigger target based on what THEY know or see. What have they heard? Did they know the players are coming? did they get any info?" that kind of thing.

Except for Beholders. Metagame the HELL out of your players if you're playing a Beholder.

 

I do the same. But I like to add Illithids to your metagame list - my flayers are mean buggers :-)

 

Mind Flayers only can be metagamed if they've gleaned into the players' minds though! ...like say, from a previous encounter or straying too close to the Elder Brain...

Yes! 

You might find this blog useful: https://www.themonstersknow.com/why-these-tactics/

Keith Amann has taken the time to analyze a lot of the creatures in 5E and has a thorough process for breaking down what their stats mean and how they can be roleplayed to fit them.

Quote from Ophidimancer >>

You might find this blog useful: https://www.themonstersknow.com/why-these-tactics/

Keith Amann has taken the time to analyze a lot of the creatures in 5E and has a thorough process for breaking down what their stats mean and how they can be roleplayed to fit them.

 
I would never have found that, thanks allot! :)

It's really case by case basis on my end. A coordinated group like a military squad might take orders from their commander to target the cleric/wizard etc first. Wild animals and creatures of similar intelligence might just attack whatever seems like the biggest threat. 

A more sporting thing like a gladiator match, might have a team battle splitting off into smaller 'duels' if it's not a fight to the death. If a particular player makes an NPC angry, they might be targeted over more practical tactical concerns. Some enemies might fell a PC and move on to the next, others might start eating an unconcious Npc or something to feed. Cold and calculating characters if they realize the party has healers, might target downed npcs to kill them and put a stop to whack a mole healing. 

I really have no hard and fast rule I just try and get into the mindset of whatever character or creature I have in the moment. 

Consider what options that creature has. Does it have only melee attacks or both ranged and melee?

Which members of the party are closest? Which ones are causing it the most pain or irritation?

IF working in a group, are they intelligent enough to go after the shooters/casters that are farther away while distracting the more heavily armored people in front?

I do my best to role play the monsters appropriately. Intelligent opponents are going to target the more dangerous PCs. I roll randomly for beasts at the start of combat. 

Don’t forget that hungry opponents such as ghouls might stop to eat the PC they just dropped while very intelligent opponents will probably target the healers first and other spell casters second. 

For monsters that aren't supposed to be especially tactically savvy, don't overthink it; just do whatever seems obvious.

I don't think what you base your choice on is all that important. More important is trying to have some kind of logic, any kind of logic, behind it and communicating that to the players. What it is will depend on the moment anyway. "You tried to hide but got spotted, that gnoll isn't going to let you get away." "You just killed their leader, everyone's coming after you now." "They've all been failing to hit the paladin for three rounds now, they're switching to what looks like an easier target." "They disdain the use of magic, so they go for the more glorious kill against the fighter." "They fear the use of magic, so they'll focus on the sorcerer first." Whatever strikes your fancy, just try to let the players know: it's more dramatic, and it can give them an opportunity to steer the encounter to their advantage - maybe the fighter can challenge the leader of the bandits, maybe the wizard can opt for more control rather than blasting, maybe the paladin can go full tank or conversely abandon that tactic altogether, and so on. Knowing the opponents' motivations beyond just 'winning the fight' can make combat more interesting than simply picking whatever action seems most efficient mechanically and going through the motions until it's over.

Whatever you do I would advise against attacking downed PCs, that’s the easiest way to get the players pissed off at you, likely to the point of quitting your campaign if you do it repeatedly.

Edit: Or if you ARE going to attack downed PCs, make sure this is 100% clear from session 0, or better yet, from when you advertise your game, an unspoken rule is that you don’t do this and if you catch your players by surprise they will get upset.

That depends on the players, really.

I'll reiterate support for Keith's The Monsters Know What They're Doing blog/book/rules.  Running your monsters more convincingly makes fights a lot harder, yes - but it also makes your games better.  It also turns out that Whack-A-Moling is a lot less of a problem in a game if your players know you are not at all going to treat 'Downed' as Time-Out Nappy Hour and their colleague who just fell over unconscious is at immediate danger of messy death.  Especially with "simple" animals, most of whom are predators and will see a downed PC as exactly the sort of target their entire evolutionary history has predisposed them towards.

Quote from Yurei1453 >>

That depends on the players, really.

I'll reiterate support for Keith's The Monsters Know What They're Doing blog/book/rules.  Running your monsters more convincingly makes fights a lot harder, yes - but it also makes your games better.  It also turns out that Whack-A-Moling is a lot less of a problem in a game if your players know you are not at all going to treat 'Downed' as Time-Out Nappy Hour and their colleague who just fell over unconscious is at immediate danger of messy death.  Especially with "simple" animals, most of whom are predators and will see a downed PC as exactly the sort of target their entire evolutionary history has predisposed them towards.

Yeah. I wouldn't make every enemy go for downed pcs all the time. 

But there are cases where it makes sense. Some predators might just tear into a downed enemy as a meal depending on the monster/animal. Intelligent enemies can probably only see the cleric get the barbarian back on his feet so many times before they decide to make sure the barbarian STAYS DOWN this time. NPCs with a vendetta against a certain PC might go out of their way to try and kill that PC, leading to the party needing to change tactics to defend them etc. 

Having every enemy spam attacks on downed pcs would get old fast, but when it makes sense, it's a good way to add urgency to a situation. And even then, depending on the party setup and what you have on hand, a player character dying might not stay dead for very long. 

Quote from AnnaAG >>

Whatever you do I would advise against attacking downed PCs, that’s the easiest way to get the players pissed off at you, likely to the point of quitting your campaign if you do it repeatedly.

Edit: Or if you ARE going to attack downed PCs, make sure this is 100% clear from session 0, or better yet, from when you advertise your game, an unspoken rule is that you don’t do this and if you catch your players by surprise they will get upset.

 Depends on the enemy. My BBEG will absolutely smile at the party while she bends down to stick the dagger in, pull out the heart and take a bite.

I try not to kill a character run by a player.  In my experience, few things make people more upset than having their character go down more than temporarily.  I don't mean that in the sense of them immediately getting back up every time they drop to zero, no, I mean after the fight is over, during the Short Rest stage.  Your idea of using skills is fine; Perception to see if they are still breathing, or Investigation to look for ways to check, like dropping a leaf over their mouth or using a mirror to see if their breath fogs it up.  There are people who try to fake death so they can jump right up and get in a backstab.

In the example of the Barbarian, which target is more likely to get attacked?  The Barbarian who keeps going down and coming back, or the Cleric who keeps making that happen?  Insight is great for figuring that out.

Good Old Session Zero is the best place to talk things over with your players.  If you want a highly lethal game in which NPCs regularly finish off anyone who goes down, tell your players so they know what to expect, if not, don't kill them unless you really, really mean to.  It takes a medium-high level caster to cast Raise Dead as is a 5th level spell.

Of course those kind of expectations should be set with players pre campaign but that goes for any approach to death. 

And in that situation, it might make sense to go for the cleric. Unless the cleric is still at high hp, and the barbarian is just barely standing from a healing word etc. KO the barbarian and then attack them again before the cleric can heal them. Going after the cleric may mean taking several attacks of opportunity. Or maybe they don't have enough movement to make it to the cleric in one turn, etc. 

This also isn't the sort of thing I pull out in every encounter. Not every enemy is going to do that. It all depends on the specific context. It can also give more urgency to players needing to tend to allies. If every enemy just kos them and moves on, the players know they generally have some time to get to them before they'll have time to fail three death saving throws, unless ther'es an unlucky nat 1 in there. 

Quote from MageMasterMalzra >>

If every enemy just kos them and moves on, the players know they generally have some time to get to them before they'll have time to fail three death saving throws, unless ther'es an unlucky nat 1 in there. 

It requires some trust in the DM from the players (though that's generally required anyway, I'd say), but having the DM roll the death saving throws without telling the players the results puts some urgency behind the healer to at least stabilize the PC.