Before Session 1: The 30-Minute Prep That Actually Matters
Read the first five rooms of the dungeon. Skim the monster stat blocks. Forget the rest.
New DMs over-prepare world lore and under-prepare the first encounter. The community's most consistent advice: read the first dungeon level (not the whole module), put the monster stat blocks on a single page where you can see them without flipping pages, and write down three NPC names with one personality trait each. That's it. Everything else you can improvise.
Don't read the DMG cover to cover. Don't memorize the conditions appendix. Don't build a pantheon. The players will spend session one figuring out how attack rolls work and talking to the first goblin they meet. Your job is to keep the game moving, not to be a rules encyclopedia. "I'm not sure, let's rule it this way for now and I'll look it up between sessions" is the most important sentence a new DM can learn.
Session 1: Start in the Action
Don't start in a tavern. Start with the dungeon door opening.
The "you meet in a tavern" opening is the most common new-DM mistake. Players don't know their characters yet, don't know the world, and don't know what they're supposed to do. The fix: start at the dungeon entrance (or equivalent action point) and give them an immediate, obvious goal. "You stand before the entrance to the Goblin Warrens. The villagers said their children were taken here. You hear chanting from within. What do you do?"
Don't explain rules proactively — explain them when they come up. "You want to climb the wall? That's an Athletics check — roll a d20 and add the number next to Athletics." Players learn by doing. Your first session goal isn't "finish the adventure" — it's "everyone wants to come back for session two." If that happens, you won.
Session 3-4: When the Training Wheels Come Off
By session three, your players will surprise you. Let them. Your job is to react, not control.
Around session three, something shifts. Players start proposing creative solutions you didn't plan for. They'll want to negotiate with the boss monster, adopt the goblin they were supposed to kill, or abandon the dungeon entirely to investigate a rumor you mentioned in passing. This is the moment new DMs either panic ("that's not in the module!") or realize the secret of DMing: player-driven chaos is the point.
When players go off-script, buy yourself time: "That's an interesting idea — give me a moment to think about what happens." Then ask yourself: would this be cool? Is there a roll that makes sense? What's the most interesting consequence? You don't need a rule — you need a fair ruling. The module is a starting point, not a script.