How I Plan Encounters
I try to avoid rolling random or wandering monster encounters mid-session, even for minor encounters. 90% of the encounters for my sessions are pre-planned. Even when the PCs do something unexpected I may have floating encounters that are prepared and changeable. I don't hesitate to use random tables for planning, but I roll the dice beforehand, the at-table randomness--if any--is determined by perception since some encounters will not start if their triggers are not noticed.
Pre-planning minor encounters let me plan for special rules and interactions between PCs, weather, NPCs, and plot before bringing them into the game. When I think about an encounter I usually look at four components:
- Composition - What do I want the PCs to encounter? This is the easy one.
- Leadership - Who is the leader of the antagonists? Are they there? What are they like? Even animals have a leader.
- Mission - If the PCs did not arrive, what would the antagonists be doing? How would they do that? How are they prepared for anyone that might interfere?
- Faction - What larger faction is represented by the encounter? What is their plan and goal?
This sort of planning has a few effects which are mostly intensional:
- The existence of a leader means that one of the antagonists is more important than the others. Depending on how the PCs interact with the leader the whole nature of the encounter may change. This may control diplomacy or a morale check.
- The antagonists are not just waiting for the PCs unless they are ambushing them. The PCs might get surprise, but the antagonists might be ready for an attack. They also should have tools and maybe even existing opponents.
- This group is probably part of a larger faction that has a longer term plan, the current group's mission contributes to that somehow. Perhaps they will take special notice of the PCs. Played right the PCs may gain powerful allies, played wrong the antagonist faction might decide to end the world!
Though we are still playing a game my goal in all the planning is to create a world that feels alive. If I need to plan an encounter in, even if it doesn't tie to the main plot, I make it tie to something--and if the PCs want to unravel it that something could become a main plot.