Any tips on how to DM well?

New Dungeon Master?

Check out the New DM Guide (it's here on the subreddit's sidebar).

Matt Colville's Running the Game series is great.

Watch Matt Mercer's GM Tips.

r/NewDM

r/DnDBehindTheScreen

r/DMAcademy

• Learn the general rules of the game, specifically the material covered in the Introduction, and Chapters 7-10 of the Player's Handbook or Basic Rules.
• Learn the rules governing the special features of each of the PCs, specifically their racial features, class features and known/prepared spells (or at least the ones that seem the least straight forward, or that they use most often).
• Keep the game moving. Don't get bogged down in rules discussions, and don't let the party dither for too long. If this happens, prompt the group to make a decision or throw a situation at them that demands their immediate attention. Likewise, keep things moving on your end; if a fight is dragging on too much and has become genuinely boring, find a way to end it or change things up (like maybe a more powerful monster charges in and kills one of enemy combatants, which sends the rest running).
• Pay attention to the players. Make special note of things that they have an emotional response to, and the things they seem bored or frustrated by. Also make a note of any important or unusual decisions that they make. These can be mental notes, but writing things down is often advisable. Make uses of these notes when preparing for future sessions.
• Acknowledge the players' choices. Use their characters' names, reference aspects of the character's appearance and equipment when describing action, or have the NPCs comment on those features. Integrate player backgrounds, and (as suggested above), have callbacks to the decisions the characters make, and have them be of consequence.
• When your players try to do something, try to avoid shutting them down. Often it will be the case that there's a very good reason why they can't do exactly what they want to do (a common one with new players is not really understanding how much can be accomplished in a single turn of combat) but if the course of action the players describe seems reasonable then try to give them at least a chance to make it work.
• Ideally, have a bunch of lists and tables handy. At a minimum I like to have a list of NPC names I can use for different races/cultures. Other lists you may wish to have include ones for: NPC quirks and personality traits, businesses, streets, town names, food and drinks, local gossip/anecdotes, and specific curiosities/magic items that the party might stumble across in a shop or treasure cache. Sites like Donjon and Fantasy Name Generators can be useful for filling out these lists; also check out the tables in the Dungeon Master's Guide and Xanathar's.
• Have a few general encounters in your back pocket in the event that you need to come up with something fast. (Same theme as the last tip: "improvisation" is easier if you've done some preparation.) A good approach might be to find some environment random encounter tables online (or use the ones in Xanathar's Guide) and pick a couple from each environment type your party is currently adventuring in -- one that's likely to involve combat, and one that's unlikely to. Then print out or bookmark the relevant statblocks for those encounters, and package them together with some ideas and notes; when you use them in play, adapt them and incorporate details that are relevant to the party's current situation.
• Try to avoid using "read aloud" text by reading it straight off the page. Instead try to internalize the look and feel of a place, and the stuff going on it, and give your players an overview of the most obvious features along with some color -- ideally something that may be emotionally evocative or set a certain tone. Personally I prefer bullet points when it comes to preparing specific rooms/areas to read-aloud paragraphs.
• Do voices for your NPCs, particularly your more important NPCs. You do not have to go crazy over the top (although that's often a good idea) or do a perfect accent. Just changing your pitch or cadence a bit, or putting some more breath into your voice, or speaking faster or slower can do a lot to give a character more impact and make them more memorable.
• When it comes to campaign and adventure building, take a mostly bottom up approach. Focus on the first settlement the party is in and its immediate surroundings, including the first adventure site they're likely to explore. Fill in the big picture campaign details later or as needed. Don't put a lot of time into developing the details of plot developments or setting elements that are 5+ sessions away from being relevant (or, if you do, do it for your own gratification and while realizing it's not a very practical and efficient use of your prep time, and with minimal expectations that it will actually be utilized in your game).
• To somewhat contradict my last point, it can help to have a few key broad strokes conceits for your larger world in mind, and a handful of details to place your local setting in context.
• Start things off with the bang. The party should have opportunities to be great heroes to someone as early as the conclusion of their first adventure, if not their first session. Even the first adventure should be more than a fetch quest (maybe the task might start off looking like a fetch quest, but you should quickly establish that the party is in the middle of something bigger).
• Be relaxed and confident. One little trick that helped me was the decision to not apologize for minor mistakes or gaffes. Don't put a ton of pressure on yourself -- while DMing really is challenging in many ways, you do not have to be a great DM to run an enjoyable game, or to meet the (likely) modest expectations of your group.

Your main job is to entertain the group, and inspire them to loosen up and entertain each other. Don’t be afraid to be goofy or foolish or melodramatic.

Make sure no one is uncomfortable with the content or the way interactions are going.

Focus on each player, then move on to the next player, so that all get a chance to shine.

Be receptive to players’ ideas. But don’t be afraid to nuance those ideas.

Don’t let arguments about rules get in the way of the narrative: make a decision, and modify it later if need be.

It is important to remember that, even though you are simply playing a game with your friends, you must not be too kind. Dying within the first few encounters is an experience we must all go through. If you have set a trap and a character trips it and all the rolls dictate that they are dead, let them die

Rules are guidelines not set restrictions

The main thing is to keep the game flowing. It doesn’t matter how good the campaign is; if you are stopping every 30 seconds to look something up in the rule book (which is what happens to most first time DMs) your players get bored and lose interest. If you don’t know the answer to a question a player asks, or you are unsure of what to do in a situation, just make something up. It’s better to do that than to lose the flow of the game

Even though the dungeon master doesn’t have a character and is actually the living embodiment of the campaign and all the NPCs, the DM is really a character by itself. When u r DM-ing, you are not yourself, you don’t know these characters (which is also important to remember because it might be wise to get the players to say a little bit about their characters so they can gauge their personalities) so they don’t know you. You could try speaking in a mysterious voice or acquiring a new piece of attire (such as a wizards hat or a fake bushy beard (or shave your beard if it is already bushy)) to let the players know that you are the DM, not their friend