There are lots of new DMs here. I'd like a thread where DMs can share their most important lessons / realizations. 

To keep it readable, let's go with 1-3 important ones in each post. 

I'll start. 

1. Does this decision add value/make things more fun? DMs are faced with lots of decisions, so adopting this mindset has been a great tool. Examples. Crit fail: Even a poor outcome should make things fun / add value. Spending time on something: Is it fun for yourself or does it make things more fun for the players? If yes, then go on. If not, take a shortcut. 

2. Always advance. Whatever you do, things need to advance, even if it's just the little RP things. Don't make decisions that hinder, drag or halt gameplay / story development. And more importantly, don't go backwards or undo things. So if things go wrong, they can lead forward to the wrong direction, but still a direction. 

3. You are the ultimate god of your game - for right or wrong. You can do anything. This leads to two subpoints: Point 1. Keep things simple and focus on the important/fun stuff. You don't need to throughly explain everything or implement too much logic or reason unless: see lesson 1. Remember to keep things consistent, though. Point 2. It can never be DM vs Players, they are on the same team - the Team of Everyone Having A Good Time.

These came to mind.

On world building

1. No need to overcomplicate things with oodles of species - Look deeper into motivation and goals and you can see that most species, even the boring humans, are quite capable of much mischief

2. Trade shapes a world. When you build it try to think about what a region would have in abundance vs what it might need. How could a political entity (say, country) change that state of affairs? How might that effect life for the common folk, for the surrounding entities (or countries). Examples might be, lots of wood and iron, long shore line, naval tradition, growing population but little topsoil could lead to martial incursions in neighboring areas for land.

3. Politics and religion: Superiority complex(es) in the ruling caste/family/religioos groupings may foster inequality, oppression, resentment, inherent weaknesses in governing forms and corruption

4. Mother Nature plays a role. Volcanic eruptions, earthquakes might force migration, martial or otherwise. Building dikes and draining land might create a completely new political entity. Deforestation, loss of viable topsoil, droughts may bring about mini collapses and mass migration (which could be led by martial incursions)

Quote from Jegblivervirkeligtraet >>

On world building

1. No need to overcomplicate things with oodles of species - Look deeper into motivation and goals and you can see that most species, even the boring humans, are quite capable of much mischief

2. Trade shapes a world. When you build it try to think about what a region would have in abundance vs what it might need. How could a political entity (say, country) change that state of affairs? How might that effect life for the common folk, for the surrounding entities (or countries). Examples might be, lots of wood and iron, long shore line, naval tradition, growing population but little topsoil could lead to martial incursions in neighboring areas for land.

3. Politics and religion: Superiority complex(es) in the ruling caste/family/religioos groupings may foster inequality, oppression, resentment, inherent weaknesses in governing forms and corruption

4. Mother Nature plays a role. Volcanic eruptions, earthquakes might force migration, martial or otherwise. Building dikes and draining land might create a completely new political entity. Deforestation, loss of viable topsoil, droughts may bring about mini collapses and mass migration (which could be led by martial incursions)

I like these ground rules a lot. Especially because these all happen on a local, global and cosmic scale. 😄 So these are important even if your campaign only takes place in a small region.

1. Keep the game moving. If you don't know a ruling, don't spend your time searching the books. That will cease the flow and immersion in the game. Instead, make your best call at what you think it should work like. If you want to search it up after the game for future scenarios, that's the perfect time!

2. Don't overcomplicate it. Yes, DMing is a LOT of work and planning, but please for your own sanity don't try to overthink things. Don't try to plan for every possible player choice, because they always will find something different. Improv and on the fly simple thinking are your best friend. Every situation can be called by simple cause and effect

3.The DM is a player too! Yes, the players having fun is the top priority in this game. The only way to 'win' DnD is when every player enjoys their time. But you as the DM are a player as much as those with the PCs! If you aren't enjoying the game, please talk to your group about it. You have just as much right to have a good time as the players you're running the game for. 

Avoid DM vs Player mentality. Everybody is on the same team - something I read recently is that the DM shouldn't think of themselves as a god or as an antagonist or anything like that: they should think of themselves as the PC's biggest fan. Your job is to give everybody moments to make them feel cool, unique, special, etc. 

For example, if you as a DM have a terrifying or powerful boss fight planned for your players, and then they manage to either significantly weaken it or circumvent it entirely with a clever idea you hadn't considered; let it happen. Don't pull BS abilities out of nowhere just to ensure the players are still challenged. If they were clever enough to figure out a way around your plans, they should be rewarded for that. 

Of course, any smart BBEG will also be watching and learning how the PCs play, and can later try to use their tactics against them somehow. But that's for a later time - give the players a chance to shine when the sun hits them. 

1. The game exists to support the story, not the other way around. Most video games exist on their own, and have a story added to them. But the rules in D&D exist to give consequences to actions, giving meaning and depth to the story. The story is supported by the game, not the game by the story.

2. The DM is on the player’s side. The DM’s job is to narrate and regulate, ensure that the player’s choices form a coherent story. Any and all details can be adjusted, changed, or even removed, so long as it makes sense from the players’ perspectives. And among other responsibilities, the goal of the DM is to let the players win without letting them know you let them win.

3. If you want your players to roleplay, you need to have them be invested in the NPCs. Give NPCs distinctive personalities and traits, make them stand out. If an NPC is memorable, the party will care about them more.

4. TIE PLAYER BACKSTORIES INTO THE CAMPAIGN. There’s no better player motivation than seeing something they wrote come to fruition within the campaign. It makes them feel special and appreciated.

These are all amazing! 😄

1.  If you open a "door" (like some random, "nobody" NPC encounter) be prepared for your party to charge through it like gangbusters.  This means a little fleshing out of these nobodies or an ability to improvise with gusto.  Players will sometimes wander so far off track at random, being ready to handle the abrupt left turn is a big lesson.

2. As God of your game, nothing is off limits.  Not to totally gimp anything or screw the party over, but if minions needed a 25 stealth to be unseen (and maybe add to the fight if the party is cakewalking it) they get it.  If a player is down to 4 HP at a critical juncture, the enemy may NO have rolled a nat 20.....If anything is critical to occur,, and God wants it to, it happens.

3. Enjoy the trips off the main quest path.  hey are a chance for your players to help shape the world they're in and be involved in "other troubles" of the land, making friends who they might otherwise have passed by (see # 1 for times this can happen)

1. Try to keep the NPC's turn in combat as short as possible. One of my first big mistakes was running a siege of Goblins, Bugbears and Ogres attacking a city and I gave tonnes of different statblocks to the cities inhabitants to try make it seem vibrant and it just resulted in a slog. Group all enemies of the same type in the same initiative and if you have enemies with several abilities or lots of spells to cast, make sure you know what they're doing before it's their turn, including what the spells do.

2. Don't worry about getting the combat difficulty right. If you're worried an encounter might be too difficult for your party, prepare an ally to arrive mid-combat who can come in to assist if necessary with heals and buffs if they're struggling. If you're worried a combat will be too easy, have reinforcements arrive. (You can also increase or decrease an enemies hp if needed mid-combat if you're desperate). As you create more and more encounters for your party, you eventually learn how to set the right challenge for them, feel free to experiment to see what fits best.

3. Official adventures don't mean the work is done for you. You have to provide maps, edit existing maps, check for wildly inappropriate encounters (-cough- Descent into Avernus -cough-) and potentially change large parts of the campaign to make it more engaging for your party. Dragon's of Icespire Peak is one of my favourite campaigns as a DM because (I believe) all the maps for encounters are provided and they all have 5ft squares.

I'd like to comment a bit on the original post, since I think I can add to the points made there.

1) Crit fails are actually not a good element to add to your game, at least not on a mechanical level. Making a table for attacks, listing potential consequences for nat 1's such as "your weapon breaks" slows down the game and makes it more frustrating for the players. In the case of some ability checks, however, it makes sense to have a crit fail effect determined in the moment if the check fails by a decent amount. Now that's what makes the game interesting.

2) Going backwards is sometimes necessary. As a DM, you might find that poorly designed elements or quick judgement calls you end up regretting can box you into a corner or slow your game to a halt. If this happens, don't be afraid to retcon as much as you need to in order to restore the element of enjoyment to your game. Do not make a habit of this, though, and only do it when it is absolutely necessary.

3) I agree with the third point, and can't stress it enough. You are the ultimate master of the game and can do literally anything to it. The players must know and respect this fact, but the DM must use this power responsibly and for the good of the game.

1. If you ever want to know if you’re an “good DM” look around your table. If everyone at the table is having fun, even if you’re not strictly following the rules, you did it right. That’s the only thing that matters.
2. It’s okay to make mistakes. Everyone makes mistakes. It turns out that’s the best way to learn how to avoid that mistake again in future. Making mistakes is not a failing, not learning from them is.
3. If something comes up at the table, and you cannot find the rule for it in about a minute, just make a decision, let everyone know that’s what you are doing, and that you will look up an official answer before the next session.

Quote from Panda_wat >>

I'd like to comment a bit on the original post, since I think I can add to the points made there.

1) Crit fails are actually not a good element to add to your game, at least not on a mechanical level. Making a table for attacks, listing potential consequences for nat 1's such as "your weapon breaks" slows down the game and makes it more frustrating for the players. In the case of some ability checks, however, it makes sense to have a crit fail effect determined in the moment if the check fails by a decent amount. Now that's what makes the game interesting.

2) Going backwards is sometimes necessary. As a DM, you might find that poorly designed elements or quick judgement calls you end up regretting can box you into a corner or slow your game to a halt. If this happens, don't be afraid to retcon as much as you need to in order to restore the element of enjoyment to your game. Do not make a habit of this, though, and only do it when it is absolutely necessary.

3) I agree with the third point, and can't stress it enough. You are the ultimate master of the game and can do literally anything to it. The players must know and respect this fact, but the DM must use this power responsibly and for the good of the game.

 Commenting on your comment. 😄

1. I partly agree. This pairs well with my "always advance rule". In combat our crit fails are usually just fails despite of modifiers. Combat is easily hindered with crit fail effects and there is a danger that the effect ruins the balance. We also use it with more creativity with ability checks but never to halt the game. So if nothing fun comes to mind, then we usually just treat it as a fail. 

2. I think these situations can almost always be fixed without undoing events or actually moving backwards. But a little detail retconning is ok if necessary. I'll rephrase myself a little: Don't for example undo the players' achievements and choices. Like if players work hard to go from beggars to heroes. Don't make them beggars again if things go wrong. Or if players get lost, don't spend half of your session wandering in the woods rolling survival. Rather have them end up in the right place but from a more hazardous direction/position etc. 

What do you think? 🙂

Lesson 1) If your players are having fun, then you're doing something right. You don't have to stick to every rule and you don't have to spend a hundred hours preparing your session in order for your group to have a good time. If they are enjoying themselves, you've accomplished one of your most important goals.

Lesson 2) The DM deserves to have fun too. The Dungeon Master's the person who has to take on all the responsibility of making sure everyone else has fun, but they shouldn't have to sacrifice their own enjoyment of the game for others. If you're DM'ing and you're not enjoying it, or a player's ruining your fun, feel free to quit the game or kick out the player. Your enjoyment of the game matters too.

Crit fails where the player takes damage or their weapon breaks etc are awful. Failing to hit is punishment enough. I've never known anyone to enjoy crit fails. 

Firstly, let me say that I completely agree with Chris. I would have said what he did, but Chris beat me to it. Shame.

1.Let your players play the game how they want it. I made the fatal mistake of writing a plot, and my players decided they wanted to play  a cult simulator, before proceeding to brainwash a village.

And uhh...that's it.

Quote from Jamie90 >>

Crit fails where the player takes damage or their weapon breaks etc are awful. Failing to hit is punishment enough. I've never known anyone to enjoy crit fails. 

Yeah these are awful. Sometimes we do give enemy minions crit fails like this. You know, those minions that don't matter so much in terms of balance. So when they crit fail, they can really tumble for the amusement and advantage of the players. 

But other than combat, I've had fun with crit fails. Like a persuasion roll that crit fails and the person completely misunderstands your point and you have to fast talk your way out of it etc. 

1. Have faith in you, mistakes happens it's okay, we all learn as we run.

2. Don't overprepare to avoid disappointment when your preps end up not used.

3. Be flexible and ready to adapt and improvise when needed, RPGs are chaotic game in a sense and can rapidly go in unexpected way.

Have fun!

1. You can split the party, but never for long, and when the party is split the point is for the action to bring them back together.

2. You should be reactive to player input, but you do need to be proactive in telling a story. There's never a point at which you can totally step back. Follow the threads players are interested in, but always be introducing complications that drive story.

3. Kill your darlings, but also be a necromancer. A plot point is only dead when you see the body, and even then, "that is not dead which can eternal lie, and with strange eons even death may die."

1. Stop talking. This one may be specific to just me, but I find myself so entranced in narration and commenting that I end up hindering player rp, which in turn makes it harder for me to know where to take the story because I don’t know what the characters want.

2. What’s in your brain isn’t in the players’. This is a commonly repeated DM rule, but that’s because it’s important. You forget that just because you know where the story’s going and you know how many hints you’ve dropped, doesn’t mean the players caught them all. Especially this is true if you don’t have a real note taker. If you give them 100 hints they’ll pick up on like. Eight of them. Don’t be afraid to plant the same information in multiple places.

3. There’s no right way to do something. For me, this one means Don’t Stop Players From Going Down Weird Paths. If you set up a problem and they start doing something completely inexplicable, it’ll end up 100x more fun if you just run with it instead of trying to drop hints that they Should be doing it a different way. 3.5. Unless absolutely necessary, spin a way for your players to succeed. My favorite sessions I’ve played in have been the ones where we faced impossible odds and Barely Won, and because I’ve been behind the screen I know the DM let a few things slide and adjusted on the fly, and that just made it all the more fun.

People say everyone should try DMing at least once, because it’ll make them a better and more receptive player, but as someone who started out DMing, I gotta say, being a player gives you invaluable insights into what sort/style of play you want to provide in the future.

1. Plan what has happened, not what will happen. Your players will always do something different, so never, ever try to anticipate their decisions. By all means make options, but if the game hinges on them picking something as an option, don't make it optional - make it happen, with or without them.

2. Don't bar holds in a boss fight. It's ok, every now and then, to say "well, this fight wasn't meant to be this deadly, I'll knock a little bit off the damage next time it hits". But when it comes to the boss fight, the players need to feel the fear. It needs to be dangerous. A Character falling in a boss fight is a dramatic turn of events; a character falling in a goblin raid on the road to the boss' dungeon is just annoying. Don't make it impossible, but if you're rolling above average every time you attack, consider throwing an attack to keep the players from thinking "oh damn, this is really unfair".

3. Know your players. I have a group who likes the game to be somewhat serious, dramatic, and with funny twists. Their characters take the world seriously, whilst the players appreciate the way I describe things as playing out comedically - notably, the Artificer using his polearm to slow a Landship. The attempt worked, and I described it as throwing the cobblestones from the road. The road had previously been demolished, so I also described a halfling, with a tub of cement and a pile of cobbles, throwing his hands up and shouting at the Artificer as he destroyed his new road. I also adapt this to reflect the individual playstyles - the Artificer is somewhat comicbook-superhero-esque, so I include these things when they act. The Monk and the Warlock are very hardcore gritty so-damn-cool type characters, so I include less of these - generally only on a failure or when I feel Comic Relief is needed for the table.