Observations on GMing Mistakes and Momentum of Play

Some sessions are going to be less energetic than others. Maybe there's a person at the table having a difficult day. Maybe there's multiple players having difficult days. Outside of the external factors, campaigns will naturally ebb from high energy to low, as the story has its beats, rising actions, climaxes, and the fallout.

That said, if a GM mishandles things, it can completely grind a group's momentum to a crawl.

Preparation, usually the lack thereof:

It's on the GM to prepare enough that they can give the players avenues of action that they can take. This varies depending on genre, but if your players can't seem to come up with something to do, chances are there's not enough prep going into the campaign.

For a dungeon crawl game you should likely have an idea of the dungeon the group is going into, a sense of the denizens, or at least the capability to improv on the fly. For games not quite running on the Felltower wavelength, you really should be fleshing out factions, NPCs, and providing hooks.

It's entirely possible to have players who are looking for a quasi-sandbox experience who will hit that wall of not knowing what to do next- even if they are fully engaged actively trying to find a direction.

If your players seem interested in a hook you improvise the shit out of that hook, even if it's not necessarily what you had in mind, or anything you had planned. That interest, that desire to explore and check things out, that's the flicker of momentum starting. A hook meant to develop sessions later is probably better used now if players would otherwise be twiddling their thumbs.

Be practical about your preparation. You really don't need a full character sheet for most mooks or minor characters. It's often times safe to not have full character sheets even for important NPCs who can be reasonably expected to not participate in combat. It's perfectly fine to only lay out combat traits for combatants, and maybe note important social skills for a character who only serves as a merchant, informant, quest-giver, etc.

Furthermore, If players aren't going to interact with it, don't make it a big focus of your preparation. Having the players being adjacent to the most interesting thing going on in the campaign world is often a bad idea, unless that most interesting thing is invariably deadly (plague, mustard gas, swaths of destruction*, etc). It's pointless to make complex magic systems if your players don't want to interact with a byzantine magical system and instead wonder why their death spells get less DPS than an assault rifle. It's a bad idea to create a massive cosmology/pantheons of Gods if people are largely interested in playing secular or atheist characters.

Leave room to react, only the most linear of games allow for planning things out like a TV show. Games are volatile. Some settings allow for resurrections, some don't. It's not particularly fun to have to ass-pull or fudge something when the dice say that a critical (N)PC just ate a x4 damage headshot putting them well beyond -5xHP. Planning too far ahead isn't practical, especially if it's predicated off actions the players are *supposed* to take.

"I don't want to prep too much until I know what the PCs are doing"

So, this at first brush seems like a chicken or egg problem. GM doesn't want to over-invest in prepping in areas where it won't matter (good), but likely doesn't prep enough for the current situation (bad). I see it as coming from a few factors.

Lack of group direction/purpose. Everyone meets in a bar and then just randomly decide to join up together and form and adventuring crew? We've all heard this cliche, and it's a rotten way of starting a campaign unless you've got a good crew of thespians who want to hammer out why everyone's working together in-character for a session. I vastly prefer having strong purpose for the existence of a group of PCs. 

"You're part of the clandestine organization Agency 17, the existence of which is hidden even from the other 16 members of the US Intelligence Community."

"Prohibition has rocked 1920s New York City, leading to ample opportunities for criminal enterprises and their members to catapult themselves to wealth and infamy."

"You're a group of Augmented Humans hand-picked by an angel to fight off the forces of Hell."

This is almost entirely on the GM, right from campaign conception. Unless you're starting session 1 with a strong sense of what the PC purpose is, or an iron-clad** way of determining it through play, you're already behind the eight ball.

Related to overall group purpose there's Lack of Immediate direction. This usually results when players don't have paths, hooks, or things to do/react to. The players might be rip-roaring to do something, stacking dice and browsing on their phones while the group spins its wheels, but without something to actually *DO* it's pointless. This is almost always a result of not enough prep.

Players need information and context to make decisions. In a linear game, some of this can be taken away ("Your next mission is..."), but for many games players are going to be on the hook for choosing their next objective or goal, and they need a solid informational ground to stand on. They need to know the situation, the NPCs, the factions, maybe cultural or geographical details. It is explicitly the GM's job to provide these details.

Other Momentum Killers:

• Allowing players to spin wheels too long, and/or rehash the same conversation multiple times while discussing plans
• Not allowing players enough time to incubate and ruminate on plans
• Not allowing players the capability to follow up on things they find intriguing
• Allowing too much focus on extraneous BS (seducing wenches, drinking plans, trivial travel plan details, etc)
• Specifically tailoring challenges so that a single player has a bad time (because once they clock out, risk of others doing the same goes up)
• Being overly adversarial with players (Are you here to beat them or provide a fun experience?)
• Not properly adjusting your campaign style to ensure it suits your players (grimdark campaign + players who just want to goof off = bad time)
• Making or allowing others to make a player uncomfortable.
• Not recognizing when things aren't working well and changing course/stopping

*A friend of mine knows someone whose Ranger's favored enemy type is Swaths

**Seriously, if you initial sessions happen and the group doesn't gel or establish a purpose, wrap things up cause you likely just scuttled the campaign right out of the gates.