Get some background ambiance, like rain or cave noises going.
When a fight kicks up, roll in some powerful music.
When something upsetting happens, slide it into some dreary piano music.

Alex Chambers
1.If youre going to do voices and accents then write down who sounds like what.
Your players will remember.
2.Dont write a story.

Your players are not characters you’ve got the option to inflict your pre written story on.
Make them roll for it if applicable, but dont straight-up deny them.
I know thatsoundsobvious but its a mistake a lot of DMs make without even realizing theyre doing it.
That doesnt make a good experience for anyone.
4.Dont introduce an NPC unless you are prepared for them to have dialog with your players.
Just because you dont think they are worth talking to, doesnt mean they think that.
Example: They lose a fight.
Instead of a total party kill, have them wake up in a dungeon and have to escape.
Fail a roll to jump a gap?
Have them fall, take damage, and find an alternate route in the chasm.
7.This is not a competitive game.
This is something I see a lot and it pisses me off.
Its the players vs the mobs, not DM vs players.
You dont want to murder the PC the worked so hard on.
It happens and it sucks, but dont attempt to.
Let the dice do the talking.
Your role is to tell the story, not to slaughter your players.
8.Dont self insert ridiculously powerful PCs for the reason of kicking players asses.
9.Dont give awesome loot fast.
If you over gear them early the fun stops.
Instead give them novelty and useless loot.
10.Take the time and effort to prep your game.
Have your rig ready as your players will always ask you questions that you might not know.
11.Get some background ambiance, like rain or cave noises going.
When a fight kicks up, roll in some powerful music.
When something upsetting happens, slide it into some dreary piano music.
Some parties are there to take it dead seriously.
Some parties want some goofy stuff to happen.
The game wont be fun if you mix those two up.
13.Dont make the players roll for every little thing they do.
If its entirely possible for them to do it, they just do it.
Only time they should roll for something is if theres an obvious consequence to them failing that task.
14.Have a mini list of names for races, places (restaurants, inns, etc.)
A big mistake some DMs make is thinking they can just read along with the campaign.
A lot of the text in a campaign is explaining to YOU how things and situations play out.
16.YOU DONT NEED TO SPEND GIANT AMOUNTS OF MONEY.
Ive seen a lot of groups put off games because they want to invest in elaborate set-pieces.
17.Most importantly: be kind.
Everyone is just there to have fun and build a cool story together.
Dont force things on people they dont like, dont make a run at kill them and be flexible.
Therewillbe situations where the players have no clue what to do and will absolutely refuse to understand your hints.
By all means, just let there be a hidden trapdoor instead of the portal and let them continue.
18.Use character names instead of player names.
It helps keep your player immersed.
19.When describing a place, mention the smell.
It adds a whole new level of immersion to the location.
21.START WITH A ONESHOT!
Do not make your first time the start of a campaign that you wrote yourself.
I have hosted oneshots where I felt so emotionally exhausted despite the players loving every moment of it.
Or plane of existence.
23.Listen to your players.
Some of the best stories come from the random threads that they will chase.
Everyone is excited to be there and they arent going to care if you arent Matt Mercer.
No one is expecting you to be except you.
25.Cheat, but only when it serves the narrative.
Also: Your players cant see your hit point totals.
Most importantly when it comes to cheating: Dont let your players know that you cheated in the moment.
If you must tell them, do so after the session.
27.Dont ever take away the agency of your players.
This is a cooperative storytelling experience, and the narrative of your actors comes first.
If they fight the guard say 300 guards just like him start running up and carry them away.
You dont have to let them die to their own ignorance.
If you arent good at that at first though, practice!
The more you DM, the better youll be at it.
30.YOU are the arbiter of what happens.
Dont let the game get dragged down into parsing the rules.
Sometimes you have to make a call and say we can go back and look up the rule later.
Use your common sense about what seems fair and balanced.