So I've been kicking around the idea of doing write-ups for your basic faction archetypes for a while now, and since the Mandalorians are a hot topic at the moment, I decided to start there.
Before we dive into Mandalorian factions, it helps to have an understanding of Mandalorian writers. Bear in mind, this is all based off my own personal observations, so if you think I've missed something or got something wrong, please feel free to provide input.
There are a few basic types of Mandalorian character:
  • Old School
  • Mercenary
  • Republic Commando
  • Legacy Era
  • Rule of Cool
The Old School Mandalorian takes inspiration primarily from the KOTOR era. In my experience, they're the most likely to try to gather Mandalorians together for Crusades, because that was a thing Mandos did back in the day. They tend to be prefer storylines involving grand conquest over smaller scale character development, but there's still plenty of that to be found if you know where to look.
The Mercenary Mandos tend to eschew larger plots and faction involvement in favor of the time honored Mandalorian tradition of breaking people and killing things for money. One of the more common choices for new writers, Mercenary Mandos typically don't have much in the way of backstory or motivation beyond the whole merc shtick. They have a tendency to mutate into one of the other categories over time, or failing that, take a back seat to the writer's other, more interesting alts until it's time to shoot stuff.
The Republic Commando Mandos take their inspiration from Karen Traviss's Republic Commando series. These guys tend to form small, tight knit groups. Though they can be found in larger factions, they tend to be more loyal to their clans than anything. Tragic backstories are common, along with heaping doses of melodrama. Though this annoys some writers, the good ones are usually welcome because they're absolute hell on wheels in a fight, thanks to the pragmatism and penchant for overpowered weaponry that was a hallmark of the books.
Legacy Era refers to Mandalorians inspired by the depictions from the Legacy of the Force series and onwards. This is one group I've not encountered a whole lot of, but from what I can gather, they're sort of a mutation of the RC Mandos. A little less old soldier and a little more hired gun, the LE Mandos strike many as being a happy medium between the types.
The Rule of Cool Mandalorians take bits and pieces of the other types, throw them all in a blender, and skim the coolest bits off the top. More serious Mando RPers often look down on them, but they have more fun, so they don't seem to care. Typically, an ROC Mando will be an alt of someone with a more serious main character who's just looking to blow off some steam. They also tend to be the most OP, blending Mando armor with Force powers, lightsabers, and whatever else they think will be cool in a fight. Can be extremely annoying, or extremely awesome. There's no middle ground.
Mandalorian Factions tend to be short lived, regardless of who starts them.
In the case of Old School Mandos, this is often because they have a specific storyline in mind. Either they accomplish their goals, in which case the story is over and everyone wanders off to do their own thing, or they fail and the factions fall apart due to infighting or boredom. Whatever the case, it's rare that they keep momentum for more than a year at the very outside.
Rule of Cool Mandos tend to have more success in terms of faction longevity, but they often have more trouble keeping interest when there's not a fight to be had. Their faction activity can be measured in a series of peaks and valleys. When there's something to fight, everyone goes in guns blazing and has a jolly old time. When there's nothing to fight, they all go off to focus on their main characters. Sometimes, a core group of writers will keep things limping along in between battles, but really the key to maintaining momentum is a steady supply of things to shoot at.
RC Mandos rarely form factions on their own. However, they often find themselves propping up ROC Mando factions in between fights, since they can do storylines with their clans until the heat death of the universe.
Merc Mandos will almost never start a faction of their own. It's probably happened, but I've never seen it. The closest they get typically is starting up a bounty hunter's guild, or something similar.
Understanding the type of Mandalorian faction you're dealing with is absolutely vital if you want to have a positive relationship, IC or OOC. Interacting with Mandalorian factions from the outside can be a supremely frustrating experience for the uninitiated. People who are drawn towards writing Mandos tend not to place a premium on diplomacy or politics, preferring instead to shoot their way through problems.
The easiest way to get along with them, then, is not to make yourself into a problem. Give them what they want. If they want a worthy opponent, try to work with them to make things fun for both sides. If they want an ally, figure out how you can be useful to them. If you want to hate your life, give them a reason to dislike you OOC and they'll see to it that every iota of fun gets trampled into the dirt. Whatever the flavor of Mando you're dealing with, they're all capable of holding a grudge, and if you mess with one badly enough, you've messed with all of them. I've seen writers who absolutely cannot stand each other put aside their differences long enough to kick the crap out of some poor soul who made the mistake of rubbing them the wrong way.
Anyway, that's my take on things. Feel free to discuss whether I'm right or wrong in the comments below.