Running Your First D&D Combat as DM
A step-by-step guide for first-time Dungeon Masters running their first D&D 5e combat — initiative, turn order, monster decisions, when to call it, and the five rules new DMs always forget.
Before the session starts
Read the monster stat blocks. Twice. The first time to absorb the numbers. The second time to plan how the monsters fight.
Print a sticky note per monster with: name, HP, AC, attack bonus, damage per attack, and one tactic line. 'Goblin uses Nimble Escape to disengage if hit.' During play, peel a sticky and stick it next to the dice you'll roll for that monster.
Have an initiative tracker. Doungim's free initiative tracker at /dnd/tools/initiative-tracker works on any browser without an account. Add every PC and monster, click to advance turns. Avoids the new-DM bug of forgetting whose turn it is in round 4.
Stage one fight, not three. New DMs over-design and the session runs to dawn. One combat at the start, one in the middle, one at the end is the published-adventure standard for a 4-hour slot.
Step 1: roll initiative
Everyone rolls 1d20 + DEX modifier. List from highest to lowest. You can roll each monster individually (cinematic) or use one roll per monster type (efficient). I recommend rolling each enemy of a kind once, then giving them all that initiative — saves 5 minutes.
Ties: higher Dexterity wins. If tied on Dex, decide DM/player order. Players going before monsters is generous; alternate ties is fair.
Step 2: the turn loop
On a player's turn, ask 'What do you want to do?' and give them about 30 seconds to declare. Don't let new tables stall — long planning sessions kill momentum.
On a monster's turn, decide its target first, declare its action second, roll the attack, narrate the result. Keep it under 90 seconds per monster.
Track conditions on a sticky next to the initiative tracker: 'Goblin 3 — prone'. Forgetting conditions is the #1 thing that flattens new-DM combat.
Step 3: rolling attacks the easy way
Monster attack: 1d20 + attack bonus vs target's AC. Hit or miss.
On a hit, roll the damage dice in the stat block. Add the modifier. Apply to the target.
Crit (natural 20): double the damage dice, NOT the modifier. A 1d8+3 crit is 2d8+3, not 2d8+6.
Saves: announce the DC, the player rolls. 'The goblin breathes fire — Dexterity save, DC 13.'
Don't pre-roll. Let players see you roll. The drama of a natural 1 versus a natural 20 is half the fun.
Step 4: when to call it
The fight ends when one side surrenders, runs, or is reduced to 0 HP. New DMs let combat drag — pick a moment to end it.
If the boss is at 5 HP and the party is at full strength, narrate the killing blow rather than rolling four more attacks. 'Your sword takes the goblin's head off' is faster than 'the goblin rolls a Death save'.
If the party is at 5 HP and the boss is at 70, the monsters who care about loot will demand surrender. The monsters who eat humans will keep attacking.
The five rules new DMs always forget
- Opportunity attacks: when a creature leaves a hostile's reach, the hostile gets a free melee attack as a reaction. Forgetting these is the #1 first-session mistake.
- Cover: half cover is +2 AC and Dex saves. Three-quarters cover is +5. Track when archers shoot into melee.
- Surprise: at the start of combat, creatures who didn't notice the threat are surprised — they can't move or take actions on round 1. Most ambushes are surprise rounds.
- Concentration: when a concentrating caster takes damage, they make a Constitution save (DC 10 or half the damage taken, whichever is higher). Forgetting this lets bosses keep their Hold Person up forever.
- Damage type resistance / immunity: skeletons are vulnerable to bludgeoning, fiends resist fire, vampires can't be turned by a low-CR cleric.
Pacing for the 4-hour session
Aim for combat to take 20–40 minutes per encounter. Six rounds is the typical length of a balanced fight.
Track real-world time. If round 3 is at 45 minutes in, the encounter is over-tuned and you should narrate to a close.
Snack breaks are sacred. Schedule one at the 2-hour mark.
Use Doungim to skip the prep
Doungim's free DM tools — encounter builder, initiative tracker, dice roller, spell-slot tracker — handle every numeric calculation a new DM needs. The 41-location random encounter tables (118,000+ scenarios) give you ready-to-run scenes when your players decide to take an unplanned detour into the forest.
Doungim is a TTRPG gaming console for D&D and other tabletop role-playing games. The web tools are the bridge to the physical console — same rules, same calculations, same monster library.