Your first three sessions of Star Trek Adventures
GMing a tabletop RPG for the first time feels like too much. Here's what actually happens across the first three sessions: what to prep, what to ignore, and when it starts clicking.
By Colin B. · Published June 11, 2026
Star Trek Adventures has a reputation for being complicated. It isn’t. The 2d20 system takes about twenty minutes to explain and one session to feel natural. What actually takes work is running your first session as GM, because running any RPG cold is genuinely hard, and no rulebook can fully prepare you for the moment a player does something completely unexpected.
This is what your first three sessions actually look like, with what to prep, what to skip, and where the game starts to feel like Star Trek.
Before session one: choose one thing
New GMs try to prepare everything. Choose one thing instead.
Choose your era. The Original Series, The Next Generation, Deep Space Nine, Voyager, Strange New Worlds, Picard — each era has a different flavor. TNG is the richest for starter GM material: the Federation is confident, the moral dilemmas are clean, and your players probably have the strongest mental model of it. TOS has the strongest nostalgic pull and a simpler political landscape. DS9 is excellent for moral complexity and faction politics, but harder to run cold.
Pick one era. Tell your players. Do not hedge toward “any era is fine” — that just delays the decision to the table, where it’ll eat an hour.
Build the ship, then the crew. In Star Trek Adventures, the starship is a shared character. Your group picks a class (Constitution-class for TOS, Excelsior or Galaxy-class for TNG era, Defiant or Intrepid for later eras) and assigns ship stats together before anyone creates a personal character. That collective act of ship creation is the first storytelling moment of your campaign, and it sets the tone for who the crew is going to be.
Don’t prep encounters yet. Download the free Quickstart PDF from Modiphius and run that for session one. Pre-made characters, complete rules summary, and a self-contained two-part mission. Zero prep required. The only reason to skip the Quickstart is if you are absolutely certain your group wants to dive into custom characters immediately — and even then, the Quickstart is a better session zero than an open character creation session.
Session one: the Quickstart mission
Run the Quickstart. Use the pre-made characters. Do not let anyone redesign or rename their character before the session — that’s a trap. Pre-made characters exist so you can start playing in fifteen minutes.
The Quickstart mission walks through most of what makes Star Trek Adventures distinctive:
The task check. Roll 2d20, try to beat a target number (set by the GM) on both dice. Success on both is clean. Success on one is partial. Failures generate Threat, a shared pool the GM spends on complications. The first few checks will feel mechanical; by the end of the first mission they’ll feel like story beats.
Momentum. When players succeed with extra margin, they generate Momentum: a group-shared resource they can spend for extra effects (asking a follow-up question, acting first in the next scene, boosting a teammate’s roll). Momentum decays at the end of each scene, so players have a real incentive to push their luck and spend it before it evaporates. This mechanic alone accounts for most of the “we’re actually working as a crew” feeling.
Scene structure. STA missions are built as scene sequences, not maps. A scene has a goal, a handful of NPCs, and one or two obvious paths. The GM sets the stakes; the players choose the approach. There’s no “right answer” to most scenes, which is freeing and terrifying in equal measure. Lean into the ambiguity: moral dilemmas without obvious solutions are what Star Trek does best.
At the end of session one, ask the table three questions: What felt fun? What felt confusing? What do you want your actual character to be? The answers to those questions are your prep list for session two.
Sessions two and three: custom characters, first full mission
Session two is character creation. This will take longer than you expect: budget two hours. Every player picks a species (Human, Vulcan, Klingon, Andorian, and dozens more), a career path (Starfleet Academy track), and two or three personal milestones. The process is collaborative and generates backstory organically. Let it breathe.
The key insight for new GMs: the character sheet has a Values section — three to five short phrases that describe what the character believes. These phrases are the mechanical core of character identity. Players can invoke a Value to re-roll a failed check, and the GM can Challenge a Value (offer bonus Threat in exchange for an in-character conflict). Get your players to write Values that are specific enough to cause actual problems. “I trust the chain of command” is interesting. “I’ll always do what’s right” is useless.
Once characters are built, run your first full mission from These Are the Voyages Vol. 1. The anthology has five standalone missions; start with the one that matches your chosen era. Each mission is three to five hours — two to three sessions at a typical pace.
For session three, the mission will be underway and the crew will start making decisions that surprise you. This is the part new GMs panic over: someone goes somewhere you didn’t expect, or suggests an approach you hadn’t considered. The answer is almost always yes. Say yes, add a complication, keep moving. The 2d20 system is designed for improvisation: you don’t need a fully realized world, just the next scene.
Common first-time GM mistakes
Every new GM makes the same handful of errors. They are all recoverable:
Forgetting Threat. The GM’s Threat pool is the other half of the Momentum economy. When players fail checks or spend Momentum recklessly, Threat builds. The GM spends Threat to activate enemy abilities, introduce complications, or have an NPC act unexpectedly. New GMs often forget to spend Threat at all, which makes the game feel consequence-free. Spend it aggressively.
Over-preparing the plot. Star Trek Adventures is player-driven. Prepare factions, NPCs with motivations, and a situation — not a script. The more scripted your session, the more it fights the players. The best STA sessions end somewhere completely different from where the GM expected to land.
Skipping the moral dilemma. Every good Star Trek story has a moment where the right answer isn’t obvious. The Kobayashi Maru is a test of character, not a tactical puzzle. Build one genuine values conflict into every mission. The mechanical hooks are already there — just use them.
Running out of Threat to spend. The opposite problem from above: stockpiling Threat so high that spending it feels catastrophic. The Threat pool is a renewable resource. It’s supposed to go up and down. Spend it when it’s interesting to spend it.
What to do at session four
By session four, the group has a functioning crew, a ship with a name, and at least one shared story (“remember when the Klingon ambassador turned out to be a shapeshifter?”). This is when the game shifts from learning to playing.
Debrief after every session. Five minutes at the end: what worked, what didn’t, what the players want more of. STA missions are flexible enough that you can change the next scene based on this feedback without the players ever knowing.
Let characters earn advancement. The milestone system gives players new abilities after significant story moments. Don’t hoard milestones — hand them out when the fiction earns them. A milestone isn’t just a reward; it’s the GM saying “that mattered.”
Start thinking about a campaign arc. After three or four standalone missions, the players will start asking about recurring NPCs, continuing threads, and consequences that carry forward. This is when you reach for The Shackleton Expanse or start building your own persistent setting. You’re not a GM running their first session anymore — you’re running a campaign.
Ready to buy your gear? See our Star Trek Adventures RPG gear guide for the rulebook, dice, and mission books worth buying first.