“…to boldly go where no man has gone before.”
According  to a number  of experts , this famous grammatical error is actually perfectly acceptable English. The infinitive may now be added to the short but growing list of things that can be split: hairs, firewood, and the atom.
Going even further, I submit that many things traditionally considered unsplittable may actually be split, including the adventuring party.
Conventional wisdom in RPGs dictates against splitting the party. In-game, the synergy of an adventuring party is stronger than the sum of its parts; this is especially important when danger lurks nearby. Above-game, parties remain unsplit largely because some players get ignored while others get GMed, and then vice-versa. Bo-ring!
But a split party should not not lead to bored players. With a little extra preparation, almost any GM can recruit idle players into a scene or encounter.
- Discuss the possibility with your players. Give them approval and even encouragement to split the party if they feel that it will help their mission. Offer rewards for good NPC roleplay, if the system supports it.
- When the party splits up, call for a brief break. Conscript a spare player or two, and draw up quick and dirty character sheets for the NPCs, with only what they need: motivation, personality, information, etc. It can be something as simple as a book opened to the critter in question and a few words on an index card. If you can, do this before the session.
- Give the NPC sheets to the players whose characters are off-stage, and game on.
- Let the players run with it. Exercise your “GM Veto Power” only if absolutely necessary.
That’s about it. Start small, and keep the meatier NPCs to yourself (especially that one with the Deep Dark Secret). There’s no reason your players can’t play the extras, bit parts, and supporting cast, instead of just the lead roles.
I’m can’t be the first to think of this. If you’ve tried it, then sound off in the comments and let us know what you learned; if not, then sound off let us know what you think.