The most critical part of setting up any long-term campaign is making sure the players are all on the same page, both with each other and with the GM. If the GM’s campaign is using a pre-built Adventure Path, it becomes important for the players to have characters that will work for the ideas involved. You don’t want to bring a paladin to a pirate campaign, and you don’t want to bring a rogue who thinks poison on their knives is just fine to something like a Holy Crusade.
Likewise, as the GM, if you’re building your own campaign from scratch, you don’t want to have to figure out adventures in Eclipse Phase for a murderous exhuman, a singularity seeker, a biochauvanist, and an AGI Rights crusader. Even with the help of Firewall as a unifying factor, this group is going to spend more time fighting each other than any X-threats. So where does this really leave us?
It leaves us with the wonders of the group template and a character creation night. The people behind the Fear The Boot podcast made a nice example of such a thing, and even provided this lovely filled-in example of how it works. The shorthand of it is that you figure out, before anything else, what your group is going to be, to give players and GM alike a framework. This won’t always work – a GM with new players or a totally new group will have to shoulder more of the burden here, and veteran players with a first-time or out-of-practice GM should be willing to put in extra effort to shore up the group.
With a pre-built campaign, the GM should either acquire or assemble a short Player’s Guide for it; the idea here is to give the players a framework to provide context when they make their characters, so they know and understand the flavor of the situation. The best ones give little perks and offerings specific to the campaign, which tie in later on so that the players have a reason to take the offerings and build around them.
Without something pre-made, the GM should tell the players roughly what kind of story they’re going for – “I want to run a war campaign” or “I want to make this a Mythic campaign” will work as a starting point. From there, pitch some more coherent ideas while inviting the players to pitch their own into the mix. At this point the group is just sorting raw ingredients, seeing what they have available and what they might want to make from it. “I want to play a kobold” and “I want to explore this part of this game world” are both good things to hear at this point.
This is where something more coherent should be forming; GMs, encourage your players to bounce ideas off each other. Does one player really want to be a valiant warrior? Does someone else want to play the kind of person who might have a reason to be around such a person, like a fragile spellcaster who might have grown up with the warrior, the quiet and insightful thinker to the bold heroism of the warrior? Maybe the warrior was the one who kept the town bully from picking on the spellcaster as a kid, and now they’re inseparable as adults. The one who wants to play a character with a rich backstory – encourage the others to find a way to weave their backgrounds with that, to give them all a solid history together.
The GM should, at this point, be tossing ideas to the players that tie them to the specifics of the setting and the future events of the campaign. Give them options to the them to the history of the location – NPCs they may have known growing up and reasons they may like or dislike them, businesses they’d be familiar with, events they may have heard of, been inspired by, or taken part in.
By the time all is said and done, the group should already have a history together, a reason to stick together, and some ties to the setting they’re in. Whether the adventure is prebuilt or home-grown, at this point the group should be knit together and embedded in the world, giving the players a sense of investment and a desire to get the ball rolling.