Brand New to DMing (Session 0 right now). Tips?

Hello.

I am DMing a campaign for the first time this year. I am running Ghosts of Saltmarsh and will be having a session 0 soon. Do y'all have any tips?

Thanks,

Joshua

The best tip I can give: You will mess up.  You’ll forget the relay important information.  Make a bad tactical call in combat.  Do things that might be unfair. Make rules mistakes. Even those of us who have been DMing for years and years still make mistakes; heck, Matt Mercer, the most famous DM in the world, has made some truly awful mistakes live on air. 

The most important thing you should do is not be too self deprecating, learn from your mistakes, be honest with your players, and listen to their feedback without getting upset.  

Go with what the players want. They never do what you expect, or what the book has told you they will do. You will need to make stuff up, and they might go entirely off-script because one of them decided to buy a viola and won't do anything else until they manage to acquire one, even when you are under an explicit time limit. (At least in my experience) Also, if you are a first-time DM, seriously consider if you want to allow homebrew characters, which I made the mistake of allowing as a first-time DM, and then not at all knowing how to handle them or level them up or anything. Also, make sure you are treating NPCs, monsters, and the world in general as if they are alive, which sounds stupid but can be hard to do as a first-time DM. You probably are fine with that, because you you are running from a book, which leads me to something else... READ THE WHOLE BOOK! Before you have your first session, if possible, read the entire book. Sticky notes are your friend here, especially if you tend to forget or overlook details of things. Above all, though, know that you WILL mess up, and if your players even notice, they will not care (if they are decent humans, at least), and will definitely not care as much as you will think they do. Just accept that you are new at this, and that even the pros mess up, and so long as it is at least 70% fun, you're doing great! I hope this helps, I had no idea what I was doing when I started DMing and had absolutely no resources to help me, not even the official books(or any books) at first, and it turned out okay.

First and most important tip: DON'T PANIC

Seriously, it's easy to get flustered and think everything is going wrong as your players come up with a plan no sane person could ever predict but never forget your players (assuming they're decent people) want you to succeed and understand it's your first time. They won't mind if you need to look up a rule, if you accidentally miss something off a monster's stat block, or if the worst comes to the worst you need to take a break to gather your wits and come up with the next step. As Caerwyn says you will make mistakes, we all do no matter how many games we've run, but so long as you're honest with your players they'll be ok even if you have to rewind and retcon something because it's totally unsalvageable (I once forgot to give a key piece of information that meant the entire campaign couldn't happen so had to go back) Just be honest with everyone.

The second tip is equally important: Have fun. It's that simple, you're a player too and you deserve to be having at least as much fun as everyone else at the table. Nothing kills a D&D campaign quite as quickly as a miserable DM, if you're not having fun everyone will know and it'll kill the entire game. Again, just be honest with everyone and if the worst comes to the worst be self aware enough to stand down and pass to someone else.

Having said all that I'm sure you'll be great, the sheer fact you're worried about delivering a good game enough to ask for tips means you care about it and you can go a long way on that. If you need help once the campaign starts we'll (usually) be happy to give help and advice and we've got DMs who post on these forums almost weekly to crowd source plot ideas so don't be afraid to ask   

• If you get stuck, feel free to make stuff up. 
• Let the players take the lead.  The story is about them, so give them the agency to decide what they do.
• "Yes, and" or "Yes, but", rarely "no".  (Generally, don't shut player ideas down outright.  Instead, let things at least sort of work, but impose consequences).
• You don't need to require a dice roll.  If the players describe a course of action that should work, just let it work.  (Example: If they describe how they're searching a room, and that method of searching would discover the trap safely, don't make them roll Perception, just tell them how they find the trap.)