I'm currently putting together a D&D game and I have most of it worked out. The only part about it that I'm still a little unclear on is whether or not the player characters should know each other prior or not. Or would that even be up to me?
I don't want to explain their characters' backgrounds for them, but how would 3–5 random strangers just start an adventure together?
There's no definite one way to go, though I prefer to have characters know each other. Here's some options and what you get of it:
How well does this work? Well that depends on whether your players are all willing to buy into "a group of strangers will work together as a team in life and death situations". It's a trope that makes up a lot of 80s action-adventure films and pulp stories.
On the other hand, when you hear about groups that devolve into thieves stealing from people and paladins going fanatical on their teammates, it's when the group DOESN'T buy into that idea.
"Ah, you're the Red Sword, I know of you!" etc. Not quite as bad as total strangers, but again, it depends on the group of players deciding to make their characters align in interest - the difference here is that with some assumed character knowledge about the other characters, you have more reason to trust them or want to work with them.
The characters all work for a similar group or cause, and so they've definitely heard of each other and have social reason to work together. This is where most games that rely on mission-based play do well in coordinating a group.
Each character knows either 1 or 2 of the other characters personally. So, everyone in the group knows at least one of the others, but not everyone knows each other personally. This still has the potential pitfall of conflict, but usually works better for bringing characters together without too much pretense.
An established group that has worked together before and at least a decent working relationship with each other. You can either have players state what that is to each other. It could be relatively new ("We banded together 2 months ago, so we're still figuring each other out, but we know we can depend on each other with our lives") or it could be after much time ("10 years of adventuring off and on together") and so on.
If the expectation is for the party to work together (and in most D&D, it is) let the players know and figure out what feels good for them with that understanding in mind.
It’s purely up to you and your players; there is no “should” here. Many campaigns start with a “session 0” where people discuss their characters, and whether or not any of them know any of the others. Typically DMs merely set a time and place, and tell players “make sure your character has a good reason to be here when the story starts,” or something along those lines.
But it depends purely on what sort of campaign you’re doing.
Lately I mostly play one-off games at conventions and such. In that context, characters who don't know each other at the beginning are pretty common. I think what's more important is that you have players who are willing to cooperate with each other. I have a friend who I don't game with anymore, because he obstructs the story and annoys everyone else under the pretext of "it's just what my character would do". RPGs are (usually) about players working together as a group. Unless everyone agrees in advance to play a bunch of treacherous backstabbers (Paranoia is all about that, for instance), that kind of behavior should not be allowed.
In my current game, I went with the cliche "a group of strangers will work together as a team in life and death situations", but I added a couple of touches to it to make it a bit more likely. First, I gave each character a fairly in-depth backstory to explain how they all ended up in the same spot at the same time. You can try to get the players to write those backstories, but in my experience they won't.
Second, I made the life and death situation SO severe that they really didn't have a lot of choice: a full-scale invasion of the city they started in, complete with burning the place down. As they were fleeing the city, they found a wounded soldier who asked them to carry a message for them, initiating the quest, but by that point they were already together and moving in the same direction.
My players are pretty compliant when I give them hints of which way I intend the plot to go. This may not work as well with a group who deliberately goes the other way when shown the road.
I think you need to ask yourself some more questions (in addition to what other good answers say):
Is it important for your story for the characters to know/not know each other?
Are motivations for adventuring and backstories important for the players or your story?
What’s the beginning of the story?
I think the more you need PC backgrounds and motivations in the story, the more important is the initial encounter or the cooperation between the GM and players in establishing why the PCs know each other.
Also, if your story needs to start in a specific way (to introduce plot or setting), getting the characters to meet each other at the same time might be a good idea.
And the fact that they would know each other doesn’t necessarily mean they’d work better together. Some examples (for low staring levels):
They know each other
PCs come from the same town/village and played “adventurers” together as kids, waiting until the youngest will be ready to leave his or her home so all could finally go and save the world. Possibly good teamwork and relations.
They are all in the same unit in the army/city guard. Sometimes they work together, but not always. They might not like each other, but be ordered to work together. Or imagine their unit is attacked while on border patrol and PCs are the only survivors. Any kind of group dynamics is possible.
They are students of one School of Sorcery (for fighter types, think of a student with a sports scholarship) and are selected to face a team of one Academy of Wizardry in a Metropolis Far Away. They don’t like each other, but something happens along the way and they need to work together. Possibly a group full of conflicts.
They don’t know each other (sorry for the cliches)
“Chosen Ones” - a powerful wizard for an unknown (yet) reason summons seemingly random characters for a quest. They all get the feeling they are special and essential, the group might work quite well.
They all travel to the same city and meet in quarantine (a standard procedure in this city or a plot hook): detained in the same room, they know they’ll leave in a few days, they can share their motivations and plan something together.
They are passengers on a ship that crashes and they all find themselves washed ashore in a foreign, hostile land… Anything can happen.
Long time D&D player and DM who has tried and suffered under all the tropes in @Bankuei's answer.
I recently found the game Technoir which has a lot of cool stuff that I am going to port into my D&D campaign.
The thing that is exceptionally good for your particular problem is part of the character creation mechanism in Technoir, see the Player's Guide. Step 4 requires the player to pick 3 (and only 3) connections which can be with PCs or NPCs and give them an adjective (affectionate, dependent, loyal, lustful etc.). The NPCs are given very short descriptions such as (from Twin Cities Transmission):
January Jade
A smuggler and gun dealer in Lowertown Saint Paul.
This could be readily adapted to D&D with more or less connections, say 4 + CHA bonus a minimum of 2 with other PCs.
As DM you give the players say 6 NPCs along with a sentence to describe them plus all of the PCs with a sentence that PC chooses to describe themselves. Then let each PC choose connections (taking turns) - the adjectives could be omitted but I think they can stimulate role-playing and back-story development.
A connection is 2-way (I'm connected to you so you're connected to me) but the adjective is 1-way (My relationship to you is "dependent" so I'm dependent on you in some way - emotional, economic, spiritual - says nothing about how you view the relationship - it was my connection so I put my role-playing hook on it for me - you play it how you like).
What I like about this is in enables the players to make the connections both with each other and into the wider world. Player agency is always a good thing.
I try not to do "assembling an adventuring party" scenes. The times I've tried this, it's been weird and awkward.
-- Thinking about it, deciding to join an adventuring group is a pretty major decision. You're literally trusting people with your life: you're going to be in combat and you'll need them to be willing and able to guard your back. You're trusting that, if you find a huge pile of gold, they'll split it fairly with you and not try to cheat you out of it. You're trusting that they won't pick a fight with someone and expect you to get them out of it. You're trusting that they'll be fun to live with and travel with for the foreseeable future. That's a lot of trust, and most people won't want to extend it to someone they've just met.
So, if everybody's character is in a room together, and nobody really knows each other, and I tell my players: "Your characters need to decide to form an adventuring party together, or the game can't move forward", it's really awkward.
Instead I just tell my players: "You guys are part of an adventuring party. You've known each other for a long time, and you like and trust each other."
This also has the (intended) effect of moving the players toward a cooperative mindset. There are some players who like to cause problems for other players -- for example playing a thief who steals from the party, or an assassin who kills party members in their sleep. When I tell them up front that everybody likes and trusts everyone else, it makes it clear that this is not the place for that sort of conflict.
So I guess I would answer your question: Yes, PCs should start the game knowing each other, unless you want a high-conflict party or you have some other really good reason to do otherwise.
