One of the biggest things I hear players in a game I’m managing say to me runs along the lines of “Well, how do you actually set up one of these things?”. The truth of the matter is that it’s really highly flexible-some games require or encourage lots of bookkeeping (Traveller makes me shudder, but even D&D likes statblocks and numbers), while others are more fluid (Vampire the Masquerade, for instance, or a D6/Shadowrun styled system). However, there are some universal things that can help.
First, the establishment of a set GM role is necessary. It doesn’t matter what role you’re in-some systems intend for the GM to have a certain attitude but the truth is that any style that works for your group is one that will work with pretty much any game. This really determines how you will tell your stories; will you be autocratic and make the decisions over what goes on in the world, provide a lot of freedom, or allow your players to really tell the story and just facilitate the rules behind it? A lot of games assume the autocratic approach, then include mechanics to allow players some influence in the story beyond what their characters can normally do, and some more storytelling oriented games focus entirely on players’ ability to manipulate the story, rather than necessarily focusing on the player as controlling a character.
Once you have the idea of how you want to run your game, you have to start thinking about how to prepare. I don’t like railroading players; if they need to do something to keep the story going, they can delay it and come back whenever they feel like in my campaigns, though this may have consequences (for instance, ignoring the dying king’s summons causes him to succumb before the players show up, and his heir won’t be happy), but there are times when you can create some content ahead of time even in a very flexible game. For instance, you can always take the time to create some stats for crucial named NPC’s and a couple generic ones, and then throw them in when necessary. You can also make maps and such of areas that the players will most likely explore, but this can be a little hazardous in a flexible campaign, particularly if you wind up deviating from the plan to such a point that the area is essentially just a random map with no relevance to the plot, or you really just make a map for a map’s sake instead of using it to add to the campaign. The old adage about no plan surviving first contact with the enemy is pretty true about planning a game; things that I thought players would pick up on instantly, or that they would do as soon as possible, often turn out to be the things that a campaign totally ignores. Sometimes, as a GM, you just have to cut your losses when it comes to developing certain things that turn out to be unnecessary; I’ve found it’s better to just put in a little more work to stay dynamic than it is to explicitly crank out a bunch of stuff but have plot holes and other such dubious storytelling to make things work.
One note about this is that the better you know a system, the more dynamic you can be. If you know how many dice a standard guard will roll, an elite guard will roll, and the Red Samurai will roll in Shadowrun, you can easily scale opponents to any difficulty that your players may encounter. The more you know, the easier it is to assign a metric for creating things on the fly; D&D is a classic example of this, where you can design a creature rather easily by simply examining what a character of a certain level would have, for instance, a level 20 half-dragon warlord would probably be looking at a BAB of 20, plus some for his strength and weapon’s enchantments. Similarly, you can find out what spells a 8th level character would be casting when selecting a power for a level 8 creature. When you get good enough, you can do this on the fly, creating things that can be implemented in minutes. Just be sure to retain consistency, or otherwise have a good reason for why said level 8 creature can breathe acid one time and fire another.
Another thing I like to do is timeline; I watch time progress in the setting very closely as part of my more free-form campaign running, which means that when certain events happen, they happen. I’m inspired partly by Avernum 3 here, which I loved for the fact that the world felt like it changed over time as the players did or didn’t do certain things, including some potentially catastrophic changes. For instance, when I start a campaign, I plan some future historical events, such as the assassination of a leader, an evil cult summoning some cthonian creature, or even just something as mundane as a particular item becoming very rare. I then stick by this timeline, and permit some NPC’s to have an idea about what’s going to happen, so that the players can work toward discovering this meta-event, but no matter what when it happens it will have consequences in the game. Sometimes I like to design several of these in quick succession, forming a “monster of the week” sort of thing, but I try not to since only rarely are my meta-events directly linked to the storyline (unless it’s “Player’s contact dies in a dubious accident” or something similar). Since these events do not concern the players directly, they remain free to go about their own paths, but solving the problems may help the players achieve their goals more efficiently. Alternatively, they may give the enemies a distinct advantage; blackouts throughout Seattle not only cripple the Technomancer’s ability to hook into security cameras and the city grid, but the cultists opposed to the players will take advantage of this as quickly as possible, especially if the party is split up. Similarly, these issues will fix themselves without the players’ intervention, so the world feels vibrant and dynamic. This isn’t crucial to a campaign, but I find that the added complexity and nuances make games more interesting.
Finally, one of the major things I do when running a campaign is make sure that all the players are on-board. When a player just sits back and echoes the rest of the team, or doesn’t really even care about the game, there’s almost always an issue going on that can have some major consequences. Maybe they don’t understand the game system very well, or they don’t have a lot of interest in the game. They could feel like another player is always stealing the show, or that their actions can’t change the world meaningfully (not always a bad thing, but usually is unless there are themes involved that include rigid social structures, such as in dystopian cyberpunk). There are a number of other things I do that encourage players to participate; I used to give a lot of character advancement for working out a backstory and plot for a character, but I’ve sort of toned that back to more of a bending of the rules-giving characters HP for skill points in D&D or allowing them to purchase an extra Quality or two in Shadowrun. I found that directly paying characters for having a story led to a power gradient that only further alienated less-attached players.
Similarly, it’s important to show players your interest in their interest in the campaign. When a player hands me a sheet of information about their character, I keep it. Realistically, we all have lives outside of gaming, so I don’t always get to do a whole lot with stuff like that (after all, GM’s do a lot of reading just keeping up on the rules), but I make sure to value player commitment through showing appreciation. After all, characters with backstories are characters that you can manipulate for your story-their long-missing sister shows up, or they have an encounter with an old (Mafia) landlord who wants them to pay their missing rent. In addition, I find that players who do this sort of thing are often planning something “sneaky”; pretty often I’ve found some equipment in huge printed out “character overviews” that is a little suspect-legal within game rules, perhaps, but no Shadowrunner without a nefarious plan has two tons of dynamite in his basement, and keeping the players from inadvertently or brazenly causing massive harm to each others’ characters is a great challenge for game masters with more “spirited” groups.