30 Days of GameMastering--Day 8!

You got it:  Day 8, Lindevi's challenge, GameMastery go!  Today's question:

How do you prep for each session?

So, once you have a solid campaign outline, your session prep becomes a ton easier.  Your first step for any individual session is to reference that document and start identifying beats of conflict.

Let me diverge momentarily.  When I studied abroad in Liverpool, my Chaucer professor taught me one singular element which drives how I game, how I write, and how I design.  He said:

"Conflict is at the root of all literature.  After all, what would King Lear be like if everyone just sat around saying, "Pass the cornflakes,"?

Most traditional rpgs revolve around conflict--whether armed or diplomatic--as the players attempt to find a solution for that conflict.  In a fantasy game, that solution usually centers on axes going into orcs and bugbears being scorched with fireballs.  In a sci-fi game, blasters are drawn and lightsabers go whoosh.  In a horror game, conflict becomes more subtle, centering on investigation and a slow reveal of clues towards a horrific end.  The pace slows, the conflict goes from a raging bonfire to a slow burn, but it still remains.

Your task as a GM is to facilitate that conflict:  to ensure that it has a steady, enthralling pace and challenges your players without overpowering them.  By identifying potential "beats" of conflict, you can then hone in on the minutia that you need to make that conflict work:  stat blocks, maps, environmental hazards, and the like.  While you can't possibly anticipate every move by your players, try to hypothesize typical scenarios that your players might take.  Are your fantasy players seeking an aquatic treasure?  Pull a few stat blocks for Deep Ones or krakenfolk, then ready a map that builds upon that conflict.

Conflict!  Conflict!  Conflict!

You can then use those beats of conflict to structure your story.  When you've figured out what the proverbial "highs" are, it becomes easier to figure out how to get to those highs, letting the PCs themselves actively seek out what comes next, budgeting their downtime and investigative inquiries as they need.

Lastly, start building in those NPCs (particularly the villains) that you painstakingly built earlier.  Use a light touch and find ways to include those NPCs into your PCs' path.  Using the above example, if your heroes are seeking an aquatic treasure, consider providing a foil for a ranger PC by including a rival relic hunter who has an edge after that treasure.  If you give that relic hunter a chance to one-up the PCs, you can drive the action from a normal dungeon delve into a race against time.  And, if the PCs lose, they have another adventure ready and waiting for them:  track down that dastardly relic hunter!

One of the best things to have on hand for this sort of GMing, I find, is a good NPC database.  A simple Google search brings up massive databases for most major systems:  Savage Worlds, Pathfinder, d20 and more.  Having these guys in hand makes your life so much easier, as the databases are largely searchable and easy to navigate!