DMing is a Performance Art
DMing is a live performance art. Your audience is small, and your piece is highly participatory, and you’re sitting in a chair describing things instead of dancing around on a stage, but never doubt that it’s a performance art. That’s why most people are hesitant to try it: they’re not worried that it will be hard to move goblin tokens around on a board, they’re anxious about performing an art that can only be practiced in front of people. You don’t have to be a trained performer to DM well (I'm not!), but you do have to think like one.
Performing Live Means Paying Attention To The Audience
The best live performers are adaptable. They pay attention to the audience and they alter the piece accordingly. If they’re running over their time, they skip a scene or a song on their set-list. If the audience is bored, or unhappy with the content, they shake it up. They’re alert and engaged.
If the performers aren’t paying attention, neither will the audience.
To apply this to DMing:
Remove physical barriers between you and your players. Don’t get buried under manuals or other resources. If you use a laptop, keep it off to the side or under the table between your feet. If you’re playing around a coffee table, you can use a DM screen, but if it would ever block view of your face, fold it up and put it away. Keep your notes in your lap. You want to connect with the players, make eye contact, seem accessible for questions and engaged in their half of the storytelling.
Pay close attention to their interest level. Even dedicated players can get fatigued if combat goes on too long, if there’s too many interruptions, or if they find themselves banging their heads against the same puzzle for too long. Most teens and adults only have a 55-minute attention span. Most of the time you have the ability to introduce a new element that changes the nature of their engagement-- a wandering monster in the middle of the puzzle, a sudden break from combat as the enemies flee.
Lead The Audience By Example
Human beings are empathetic, social creatures who unconsciously copy other humans around them. Now that you’ve thrown out your DM screen and they can actually see your face, they’re going to be influenced by what they see without even realizing it.
Model the energy you want your players to feel. If you’re tired and mumbly and distracted, your players will be, too. But if you show enthusiasm for the game and get excited about the choices they’re making, they’ll find themselves perking up.
For scenes where you want to evoke a certain emotion, you need to get invested and put yourself in that emotional space. Even if you aren’t very theatrical, the main trick to making someone feel something is the start by feeling it yourself. Your physicality and your voice will change automatically, and communicate the content to your players more effectively than if you tried to evoke it without engaging with it yourself. And again, if you’re not going to get emotionally invested in this scenario you’re laying out for them, why should your players?
But Let The Players Influence The Tone
A word of caution, though: If you’re running a scene which is supposed to be frightening, and you’ve put yourself in a frightened headspace or physicality to communicate that to them, but they’re having none of it (“I ain’t afraid of no ghosts!” shouts the fighter, coating his fist in holy water so he can punch the malevolent phantom with the melting face) don’t try to domineer their emotional response with the tone you want to set. Change your attitude to match theirs, because they’ve decided to take your offer of a game about being scared and turn it into a game about punching ghosts. Punching ghosts is a fun game, it’s the game they WANT to play at that moment, and it will be a more fun game if you lean into it with your performance and descriptions.
You can try raising the scare-stakes a few times to see if they change their minds and want to play the get-scared-by-ghosts game, because they might decide they do, but if they keep rejecting the offers, roll with their tone. Likewise, if they start to have second thoughts about their “punch-ghosts-first” policy and express some fear without special effort from you, that’s an invitation for you to sell them the frightening performance.
The fact that the game responds to the players in a deep and poignant way is the one, gigantic advantage RPGs have over video games and other interactive fiction.
Don't Get Hung Up On Bombing
When a performer's act goes over poorly, they feel it on a deep and personal level. The same goes for when you're DMing. Sometimes, after a particularly unproductive session, you walk away with a bad taste in your mouth. The parts you thought would be exciting were flat, you couldn't command the group's attention, and everyone felt lightly agitated and unengaged.
Ultimately, a certain percentage of the time, your performance isn't going to live up to your hopes and dreams. Sometimes the audience is hostile and there's not enough charm in the world to win them over. Sometimes you try to read the room and your instincts are dead wrong. Sometimes you're just having an off night, or the venue is full of disinterested bystanders.
The important thing is not to get discouraged. Make a short list of the problems you encountered and a few strategies to try next time to address them. Then stop beating yourself up over it, because the reality of live performance is occasional rejection.
Be as present as you can.
Pay attention to your players.
Be as invested in the game as you want your players to be.
Learn from your mistakes, but don't obsess over them.