I'll be DMing my first session soon and I'm very nervous about it. Does anyone have any tips for a new DM? Thanks! <3

There are a lot of tips out there, I'll give you mine!

• Making a call is better than getting it right. If you're in a combat and someone says "I will run forward, shove them over and then attack with both my swords!", it's better to make a call as to whether they can or cannot do that and then keep the game flowing than to stop the game, open the rules, try and find that one rule the player insists that they've seen and knows it lets them do this, and so on. Make a note of what they did and look it up after the game, tell the players what the correct call was, and if needed, tell them it will be working by the book from now on. It's not going to ruin the game if one player spends one session doing one too many bonus actions because they've misread a line which said they can only do it once per long rest. It might make the encounters too easy for one session whilst they're learning, but it's better that the session be fun and then you correct it after than it be strictly to the book and everyone sits around trying to read every rule all the time!
• Plan for the things which led to now, not the things the party "will" do. As soon as you say "The party will talk to the bouncer and find out etc.", you can be certain that they will either ignore the bouncer, or pick a fight with him, or try to seduce him, or do absolutely anything except what you need them to do to progress the plot. Instead, say to yourself "The bouncer knows >important info<, as does the barman. The waitress knows that the bouncer overheard something from the barman, but he wouldn't say what." Now you have 3 facts, which nothing the party does can invalidate, and they have 3 ways to find out where the info is.
• Never put plot progression behind a riddle. Riddles are cool, but they tend to be hit or miss - people either work them out, or they don't If the next bit of a dungeon relies on the party working out a riddle, you'll either have to spoon-feed them the answer, or make a different dungeon if they cannot work it out.
• Get organised. I have notes lying around everywhere, for different campaigns and adventures, and as time wears on I forget more and more about them. Don't be me - have a dedicated book for it, and religiously write everything you write in that book, with notes. Don't just write "Dagger - cursed", because no matter how much you think it makes sense now, in 3 weeks when you next avoid scheduling conflicts, you will be asking "What dagger, who has it, what curse, where even are they, where are my notes on this?", and that will make you stressed and enjoy the game less!
• Do a session 0, which is where you ask the players what they want from the game, and find out what the characters want from the world, and then get them to amend characteristics you don't think are going to work together. It can be easier t obuild a party than to build 3-5 characters and mesh them afterwards. Get everyone to build characters together, so that they don't rub each other the wrong way! 
• Try to keep your first session simple. Don't try to have the party meet, then travel across 2 different types of ground using travel rules, then have to barter for stuff in a local town which you now need names for every shop, then go to a dungeon and fight enemies in a room which moves all the time etc. etc. Pick what most of the party wants to do (see session 0) and then focus on that. the party wants to kill monsters - so give them a quest to find and kill these monsters. Chances are, the things the players are most interested in are also the things they know most about. If the party is built for fighting and you start playing with mysteries, roleplay and deception, with etiquette for removing armour indoors and all those fiddly bits, they will be lost and won't be able to help you. Most people know what their characters can do  fights, so give them fights!

I've seen a lot of advice saying to run non-homebrew stuff first, which I didn't listen to and I think it's going well enough for me! I would avoid giving anyone magic items until you know what their characters can do in the first place. Get familiar with the game, the players, and the characters before you start throwing them things which could turn out to be game-changing.

Have fun! DMing is great fun, and once you're past your first session, you'll be a lot more confident!

At the end of the session, have the party decide and tell you what they plan to do next, so you can prep for it. 

Have a list of names ready, so when they try and talk their way past guard No. 4 or random shopkeeper, you’ve got something to call him.

If everyone is having fun, you’re doing it right, even if you’re not strictly following the rules.

If you’re not good at accents and voices, don’t do them. In this case, not doing one is better than doing one poorly — it can take the players out of the moment.

If you're running a module, prepare for the party to go run off somewhere else and derail the story 

If you're running homebrew campaign, don't get too attached to your favorite npcs because it is likely the party will either kill or ignore them 

For me it’s all about expecting the unexpected. Try and get into a spontaneous mindset. As people said above, your players WILL do things you didn’t plan for. They will misinterpret signals and they will do their own thing. And that’s the magic of DnD. Lean into that freedom and react on the fly. It can be scary but it creates the best moments that people will remember long after the session is over. 

One random utility tip is try to find a way to display initiative or if not, call out the next turn when you call out the current turn (eg: “Jim it’s your turn, and Louisa you’re up next”). Keeping combat moving, brisk and flowing tends to be key to people staying engaged.

Try and relax and have fun. It’s a game and you’re playing it too :)

Let there be silence, don't feel you have to fill it. Its the small moments that matter, the cool story is nothing without the interaction and stuff. Not balancing a combat quite right at first is part of the experience, it comes with time.

Don't forget to have fun, you're there to play too.

Break the information you need to give out into two categories - 1) must know to move the plot forward and 2) optional info that gives the players an advantage. Then make sure the "Must Know" stuff comes up regardless of skill checks or whatever. I have seen many DMs flounder because they locked the plot's next step behind a history check or whatever and then the party proceeds to fumble the next 3 history checks.

In other words, only make failure an option in situations where you know what to do when the party fails.

Quote from scatterbraind >>

Break the information you need to give out into two categories - 1) must know to move the plot forward and 2) optional info that gives the players an advantage. Then make sure the "Must Know" stuff comes up regardless of skill checks or whatever. I have seen many DMs flounder because they locked the plot's next step behind a history check or whatever and then the party proceeds to fumble the next 3 history checks.

In other words, only make failure an option in situations where you know what to do when the party fails.

This is some very good advice. It goes hand in hand with not making people do skill checks unless there's a relevant point to it. If your rogue, with no time limit, says they will pick the lock, then instead of having them keep trying over and over until they get the DC, instead make them roll once and use that to establish how long it takes them. If it really doesn't matter, don't even have them roll, just say "yes, you pick the lock" (in a more interesting way, of course!).

If you make the next step revolve around lifting a beam, and there is no way past without lifting the beam, then make sure that the party lifts the beam. Don't make the plot stop for a reroll, it's not needed!

Run one shots or short modules. PCs are Players Handbook Only for the first six months of gaming. Big mistakes like death, too much cash, etc admit to and fix off board. Minor mistakes admit too but don't worry about. Sorry I hit you with the 20D20 fireball John but you only took 40 pts of damage last session, opps. 

hey  me and some other people need a dm is anyone open