1. Funeral: I once started a group of characters at the funeral of a great hero. Each character was there for a different reason. One was the hero's granddaughter. Another was apprenticed to an elf wizard who had been the hero's best friend some 50 years ago. One was a young priest, sent to deliver his first burial ritual, and the last was a dwarf who was magically teleported in from a far away fortress to use a magic hammer needed to engrave the date on the hero's specially prepared sarcophagus.
B.
If the Campaign starts in a big city that is racially diverse, the PCs can all start off as low-ranking members/officers in the city's many specialized Guild Acadamies for different Classes / Player Roles / or Power Sources.
This can be taken a step further by really allowing a PC to "go to town" on their background when classes can combine the fundamentals of different Power Sources. A Swordmage, for example, may've been in the Fighter's Guild for a short time but noticed a much stronger facination towards magic. Thus transfering to the Mage's Guild/Academy to learn how to wield the magical arcane energies through the sword.
Sure, let them tell you what they did the night before and then slap them in prison with a great walloping headache.
Nothing bonds parties like being set up, escaping a prison, evading and the authorities while locating the culprits.
A. Feel that they would work well together. Or
B. Are from different parts of the city and don't know that the other officials are sending people to stop the rioting.
18. It's Your Birthday/Wedding/Bar Mitzvah/Etc Party! Similar to the funeral idea but less depressing. A character or an NPC is having a celebration and all the characters have either been invited or are guests of an invitee. Then something happens! Who springs to action?
To do this properly, you create a small scene, perhaps 2-3 short encounters, that enable the characters to meet and work towards a common goal. It's even possible for some characters to be on opposing sides at the beginning, as long as they can come together by the end.
Next, you "fast forward" to a few years after the war is over. Each player can summarize what their character has done during the intervening time. Now all you need is a plot element pulled/continued from the intro scene to use as an excuse to reunite the "war buddies".
Stolen from Eberron Campaign Guide
Each one wants to be with the next, but not the former. It's like high school but the halloween dance has a real witch (and I'm not talking about your math teacher).26. Magic bound The PCs are bound by a magical meaning and if they want to get freedom back, they have to pursue the same goal.
10. You all wake up the next morning in prison
Sure, let them tell you what they did the night before and then slap them in prison with a great walloping headache.
Nothing bonds parties like being set up, escaping a prison, evading and the authorities while locating the culprits.
A variation on this I'm using is:
"The prison guard lies at your feet, blood soaking into the dirt. You only have a few minutes before one of the other guards finds you standing over the body of his comrade, the murder weapon in you hands. Why are you here in a prison camp? What made you kill the guard? What do you do next?"
28. the bounty hunter strikes an infamous bounty hunter lays claim to a seemingly-defenseless NPC in broad daylight in a lawless frontier town. immediate questions for the PCs: is bounty hunting acceptable here? why would such a high-profile bounty hunter attack this poor guy? do they want to intervene, or let rough justice take place?
29. invasion!. the town in which the PCs happen to be is unexpectedly attacked by neighboring power/orcs/etc! in the ensuing chaos, the PCs find themselves taking shelter from the siege weapons in the same tavern. immediate questions for the PCS: who the heck are [attacking force]? does this community have something they want? how do we avoid this army--or do we want to rat out the town, work out some kind of deal?
30. on the refugee trail. a variation on the previous: the PCs are getting the heck outta dodge by night because of a tip-off of an approaching hostile force. but in the chaos, the part of the caravan with the PCs takes a wrong turn and winds up in a winding ravine and encounters a scout/expeditionary force of hostiles. immediate questions for the PCS: same as previous, plus: how the heck did we get separated from everyone else? is anybody else in this bunch combat-worthy?
31. You Awaken In a Room
There's always the tried and true method. Your party awakens in a room, gears grinding in the background, a door nearby finishes shutting mechanically and locks bolt into place... and the room starts to fill with water. What do you do?
32. In Media Res - Our intrepid adventurers are standing in the middle of a long, wide stone bridge hundreds of feet above a crystal-clear lake at dusk. Bodies of soldiers and monsters alike are strewn about like trash in a landfill. A shrouded, dark warrior strides forth on wings of fire and engages the heroes in combat, defeating them to a man. Left bloody and near death, the adventurers watch as he soars skyward and rains down a meteor swarm on the bridge, rending it asunder and sending them plummeting into the water below. Back-track one month before this event, when they awake after a troubled night's sleep, and meet each-other. Strangely, they all seem remarkably familiar for being perfect strangers.
33. when ragamuffins strike! the PCs are all walking down different very crowded streets in the same city. they must pass a passive DC 15 perception check to avoid being bowled over by a running child, who's being hotly pursued by a wealthy-looking merchant screaming "thief! thief!" an acrobatics DC 15 or athletics DC 15 check will allow the PC to move through the crowd.
immediate questions for the PCs: is the kid really a thief? is this a setup? how is that kid running so darned fast? why does it appear nobody else is paying any heed?
34. Death! The player characters are all snatched from the moment of certain death by a powerful and evil cleric who charges them with tasks to repay him for their lives.
35. Contract! There is this place you can go and get a job. The fewer questions you ask the better the pay. The more danerous the job the better the pay.
36. Defenders Call! Each member of the party is chosen for their devotion to preserving lfe. Each player is delivered a message via druid animal companions to meet at a sacred place and be given guild amulets like in Fable. If one person teleports it triggers the entire party's amulets as well. Hive mind and telepathic communication. One free resurection included.
Haven't tried that last one actually.
37. Lone Agents, Asked to Work Together: Each PC is an agent for the same organization - secret or not - and works alone*. He's called in by his superior or contact, and told this time he'll work with other agents for a special mission. Hence the get together of the PCs. This has for an advantage to ensure the PCs have all the same allegiance...or do they?
* For the Dark Sun setting, this organization can be the Veiled Alliance, and the PCs are all lone terrorists working to bring down the sorcerer-kings and their defiler lackeys, and protect Veiled Alliance assets and members. The DM can have fun introducing each player to his character and his background by making him run through - alone - one of the missions he's supposed to have done prior to this one. Make it a one-nighter, giving each player a unique memory to later share and perhaps a piece of the puzzle as to the reason they were all asked to work together on this mission.
38) Reunion. They are all from the same town, and grew up together. They vowed to come back together after a time (five years?), and during the reunion trouble ensues...
39) Vacation at last! The heroes are all at a vacation resort, enjoying some well-deserved time. Except perhaps the rogue, who probably snuck in. Maybe the Druid is actually employed by the resort to tend to the animals and plants...And the ranger is actually a tourguide? I had some PCs that wanted to do this one (druid and ranger, go figure) and the rest of the party went to the resort to "relax." And then a terrible wave of creatures crash a nighttime party at the resort....
40 - Working a different thread of the same mystery. A person was murdered (or whatever), and the characters all have different stakes in it, working towards a similar resolution. Individuals will become small groups, small groups become larger groups, etc.
41 - Competitors/Rivals with common cause. Nobles often hire adventurers for nefarious or questionable purposes and many nobles have a pool of them that they call on. If the nobles decide the adventurers are politically dangerous - they might decide to remove some of their more used adventurers.
42 - Applying for the same job... and denied. Commiseration over booze becomes friendship becomes common cause.
38) Reunion. They are all from the same town, and grew up together. They vowed to come back together after a time (five years?), and during the reunion trouble ensues...
*coughcough*Dragonlance*coughcough*
43) Panic! The PCs are all staying in the same inn when Evil BBEG stirkes searching for something (see Weakness) The PCs get together and fend off his minions.
Divine inspiration: One of the gods (I used Ioun recently) appears to the party members, by ones or twos, and asks them to perform one or more tasks. These tasks, of course lead them to eachother, but not necessarily on the same side!
45. Siblings: The PCs are of the same mother and father though have not lived under the same roof. Each contacted by mother or father (take your pick) and asked to come right away.
46. Mysterious Letter: Each of the players recieve a strange, mysterious letter from an unknown source, appearing out of nowhere. The letter is cryptic and seems to hint to future events for each of them, leading them to each other, and eventually leading them to prevent some grand disaster in the future. And during impossible to escape or survive situations, the letters hint towards a hidden item, a dark secret, an un-thought-of idea or theory, or something of the sort, that lets the players escape these situations. In time, the players should hopefully find out that the letter is from each of them, albeit in the future, and now the players must obtain the power neccessary to not only stop the disasters, but to be able to send the letter to their past selves so that the cycle can continue, and so that they won't destory Time itself.
Or something like that.
Knighthood: Even rouges and the like can be conscripted! You are all -somehow-members of the same fighting legion.
48. Magically Summoned: NPC wizard/noble/sage/anything uses powerful spell/ritual/artifact/ anything to summon the precise group of people he needs to do job X. EG: one by one the characters are spit out of the wizards magic well.
49. magic store players started level 3 so all had access to some megical items had them make characters but not select magic items yet, droped them in a store where they could buy their magical items together, store had one item of each tipe no players could have an identical item