It’s one of the oldest tropes in gaming: never split the party.
Logically speaking, it’s because most every system is built to encourage cooperation by balancing powers between character types. Splitting up a well-nit group of niched halves leaves a lot more room for getting blindsided when danger strikes. Realistically, it’s more often enforced because split-screening is a lot of work for GMs, and we tend to apply a liberal amount of negative reinforcement to subtly suggest our players not do it again.
But let’s go with the niched halves thing. It sounds better.
Like it or not, split-screening is often necessary to avoid the on-rails feeling of forcing everyone to do everything as a group. Just like the players themselves, characters occasionally need a break from one another, and some activities are best done solo or in small groups.
…I meant stealth, you perverts.
From a GM perspective, there are actually quite a few out-of-character benefits to letting players split up and attack a problem from different angles, or to attack several small problems at once. It can speed things up when you need it, assuming you don’t let it slow things down.
But it is a tricky dance to manage without frustrating anyone at the table (yourself included), and like most things in your GM toolkit, there are several ways to attack it (and hope you win on initiative).
Speaking of initiative, the simplest way to make sense of several characters in several places doing several things at once is to keep things in initiative order, whether you’re in combat or not.
If the PCs aren’t fighting something, just widen the span of what a round means. If a combat round is a few seconds, make a split-screen round a few minutes. It’s the difference between actions and tasks. Just make sure the tasks don’t take overlong out of character. The process of turn-based play slows things down by it’s very nature, and everyone else will be waiting for their chance to act if you let the scene linger too long on one task.
Depending on the size of your group (or the size of the groups they’ve split into), it may also be worthwhile to group initiatives by area. Handle all the actions in one area (PC and NPC alike) in their own relative order, then switch to the other side and do the same. It creates less of a neck-breaking feeling bouncing through several arenas in rapid succession. Each location still forms a coherent small scene before moving to the next. Grouping initiatives also gives those in the inactive group(s) time to scheme and plan among themselves while they wait for their turn.
If you’re the battle mat type, be sure to divide the map by group so that everyone can keep track of what they’re doing even when they or their group isn’t active: it’ll be confusing enough switching arenas back and forth without a visual reminder.
Since you lose real estate dividing the active section of the map in half, you may find yourself redrawing more often, especially if you’re drawing at scale. Keep one or more spare, note-free copies of the map on paper so you can task the players whose turn it isn’t with redrawing their half, freeing you up to keep running for the active group.
In fact, you really should have a spare, note-free copy of the maps you’re using whether you’re split-screening or not. But that’s a topic for another time…
At this point, an important distinction should be made between the party splitting into two or more semi-uniform groups as a collective decision and one lone yahoo riding off on his own into the night. If you have a player who goes off alone of their own accord when it seems like the party would just as soon keep everyone together, don’t be as concerned about the even split.
Remember the 45-minute rule. The player who split off alone doesn’t get as much time as the whole other group he left behind, just his own personal share. Don’t bother with initiatives, it will only slow things down in a one-to-many scenario, but keep a count of the real time that’s passed. In a five-player group, the person who went off alone gets 1 minute to everyone else’s 4.
Bear in mind, if the party sends a scout ahead to investigate something, there’s no need to punish them: it was still a party decision, or at least one the party is amenable to. The rest of the group may actually be actively listening to the intel the scout uncovers, so while their characters aren’t there, the players themselves are engaged in the scene and still “grouped” with whomever they sent off alone.
Of course, if you are the reason they felt it necessary to scout ahead (because they don’t want Yet Another Ambush or Exploding Floor Trap), throw a bone to those left behind while the scout scouts. That is to say, give the scout the explosive floor trap to disarm while the rest of the party gets ambushed so that no one is tapping their foot for long. And then maybe cool it on the “suddenly: kobolds!” action for a few sessions…
The last trick when split-screening is to try to weave the separate threads together whenever you can, and not just at the end of the scene when the party rejoins itself. Have the actions of one group or theater affect the situation of the others in real time.
For example, if a PC in the group who’s trying to retake the power plant throws an enemy mook into the breakers to electrocute the guy, you might have the lights go out across the compound, where their friends are pinned down in a firefight in the garage and in need of an escape. In a large puzzle dungeon, disarming a trap or opening a door in one section might close a door in another or otherwise alter the situation without the PCs responsible knowing.
The PCs may not be aware of each other’s actions, but the players are, and showing the connected lines between them still creates a sense of unity while their characters are apart. It also gives them reasons to pay attention when they or their group aren’t up, keeping them engaged and interested throughout.
Don’t be afraid to make use of the fog of war to help make split scenes memorable moments for all players. Perhaps my favorite trick is to have each group notice the approach of a handful of well-armed individuals across a dark or dust-riddled room, without telling either group that it’s the other PCs they’ve just spotted (and simply can’t make out clearly).
Nothing says “superhero handshake” like a fireball out of nowhere that you just heard the guy you’re sitting next to cast.
Everything from information gathering to combat infiltration and rescue can feel faster, more exciting and more natural to the PCs if they’re allowed to break up and handle it their own ways. Done right, a GM can seamlessly juggle several theaters of action at the same time without the players ever feeling like they aren’t all at the same table with each other, having fun as a group.