As a GM you've spend the last few weeks prepping for a new campaign. The players are rolling their character, buying equipment and milking he rules to get any advantage they can find. With this done, the GM needs to find a reason for the players to meet, to be together and to trust one another with their lives. Some may gloss over this gathering or even skip it. Trying to find new reason for the party members to be together can be daunting and not all the important in the larger picture of the campaign. But I think the introduction into the campaign is important and a GM should take some of that prep time to consider how and why the party is formed.
Relatives: The players know one another because they are family. In this case the GM should develop an outline of the family history. Develop the history enough to sneak some family secrets and rivalries and jealousies. Often overlooked, families can be a great source of inspiration and motivation. If the players are all related it relieves the burden of 'how they met'.
From the Same Village: This version is pretty much the same as Relative above and can be combined. Again the characters come from the same background and shared the same experiences and will probably have similar motives. A couple of locals trying to make it big, trying to break out of the everyday toil of everyone they know.
Slaves: This one is a good one, I think often underutilized. Players begin the career as slaves, whether they have been recently captured or been slaves all their life. They will have a common goal to be free. A good example is Spartacus. There are a lot of potential adventures leading up to an escape and dealing with a player's master. A twist on this version could be that the master could see the potential of the characters and become a patron. Of course he would get a substantial cut of the treasure, but if you run a game where slavery is an everyday and everyone occurrence than all slave owners do not have to be whip wielding tyrants. For example, most of the players I know that got involved with slavery bought them to release them. Examples of this would be A4: In the Dungeons of the Slave Lords. This is definitely not for every party.
Guildmates: Professionals in the same trade often know one another. They would meet in guild halls, markets or in their travels. Guilds do not have to be focused on a craft profession, but can be for any common interest. Some of the examples I have played in using this have been theme campaigns where everyone played a city guard, a mage or thief. The great thing about these type of campaigns it forces the GM to develop that guild, they way of life in great detail and it often happens with a great deal of assistance from the players.
A Gathering for a Greater Purpose: The Fellowship of the Ring. I don't think I need to explain this further. Tolkien has already done that. One campaign I ran used this as the glue for the party. A party who did not like one another, there were rivalries and hatreds, but because the one purpose was more important than those things they begrudgingly worked together. It made an interesting party dynamic.
Summons by a Lord or Great Power: A lord of the manor, baron, king, priest or a god gathers the players because of their abilities or their potential abilities. This often mingles with the above, for a Greater Purpose, but it is not limited to it. Could be the baron is having problems in the eastern villages with raids and the king recently made him provide double the soldiers so he doesn't have the manpower to deal with the raids. Maybe by chance or reputation the players are gathered to deal with the situation. These can be a one shot or long term situation, but either way it is enough to introduce the players to one another. An example I would use would be King Arthur in the early years. When the Grail Quest began it would fall under the Great Purpose category.
Location, Location, Location: Example for this is B2: Keep on the Borderlands. The reason why the players would meet there is that is happening spot. A place to make a name for yourself. If a village or keep is known to have a dungeon close by and people are hauling treasure out it won't take long before others gather to get their share.
Stranded: I was reading over the latest adventure path for Pathfinder and the initial set up is the players are shipwrecked on an island. So they have to scavenge what they can from what is washed up on shore. I like the idea of that. And the very cool thing about this one is if you need to introduce a new player just have them wash ashore.
Greed: Sometimes it's not difficult or a majestic purpose. It's just money. Don't care about the purpose, don't care about the fame, money is the goal. Money it the end.
In Media Res: Or 'Into the middle of affairs'. Or 'roll initiative'. Imagine the players finish all their little details for their characters and they think the GM is just going to east them into the game with a stroll through town or a tankard at the tavern. Oh no. The GM places them right in the middle of a battle where they must join forces to survive the encounter.
Forgedaboudit: And of course the GM can just forget about romancing the players together and just have them together because that's the way it is. For one shot adventures this is what needs to be done.
A few tips I would give GMs new and old if they haven't tried this before.
- The first is to run the players separately for an adventure or two. This allows them to get a feel for the character, the world and develop a background. So when he joins the party he already has a idea of how he approaches things in the world.
- Second, if you are playing with a point base system like GURPS, allow the players to rearrange points if they wish during the first two sessions. Sometimes the idea they had when developing a character doesn't play out that well with the party. So allow them to tweak it if they wish.
-Third, I think it's the GMs job to develop an outline of the character's background so it fits into the world, doing this of course with the player. And then the player has the outline can fill in the details. This will give the character a knowledge of things so a cleric knows not to pray in the middle of the market because that is against the atheist baron's law. Simple but important things.
-Fourth, don't get too wrapped up in party balance. It may help the player tremendously to have a cleric who can heal them, but if they don't they will have to figure out a solution. Maybe it will be to buy a ton of healing potions or hire a cleric to travel with them. Allow them to find a solution to the problem. Makes it more interesting.
-Lastly, do not get too fancy with introducing new characters into the game. I once had a GM, I won't mention any names *cough* Rob *cough* who tried to introduce my character into the game by imprisoning me in a coconut. I don't think I was too subtle with my critique, "I think that's the dumbest thing I've heard." But I went along with it anyway. The party found the coconut and didn't open it. So I spent the game trapped. Rob tried to get them to 'open' the coconut but the party was having any part of it. Please GMs, do no put imprison your players in food.
Not sure if that last one was a tip, but I was remembering the incident and thought it was funny.