I'm going to try to DM Curse of Strahd for a bunch of new players. I'm pretty new myself. I have played about 6 sessions total of D&D my entire life, all 5e.
Do you experienced DMs do a session 0? I was planning to just follow this guy's guide.
Not using any software or anything like that, except maybe some sound effects from this website.
Professionally produced, user supported, advertising-free ambient audio.
tabletopaudio.com
Any advice for a new DM? What rules should I focus on memorizing so I don't slow things down looking stuff up?
curse of strahd is good stuff. session 0's are great for new parties and new players so it's a good idea to do it. it's a great time to go over everyone's expectations, including yours. ask the group if they are looking for more rp opportunities, more tactical combat focus? are they looking for a difficult experience where character death is a very real possibility or are they looking for just a fun romp through transylvania? as the dm, what are the players looking for from you? a hands off approach where you just tell them what they see and let them figure it all out or do they want you to hold their hands and keep things on rails? more or less interparty conflict? and if less, at what point do they want you to step in and redirect things?
if you know the players fairly well, some of that you may already know and have a good feel for, but session 0 is the perfect time to make sure everyone's on the same page.
as far as rules go, i'd make sure you were familiar with combat and spellcasting rules. there are certain classes that supercede the game rules, but it's good to know the basics first and then if something doesn't sound right, you can always just have the player read the spell or ability they are trying to use.
for example, with spellcasting you can only cast 1 leveled spell on your turn. if you cast a leveled spell as an action, you can only cast a cantrip as a bonus action. where this gets messy is with sorcerers and the quicken spell metamagic ability. this lets you turn a spell that has a casting time of an action to instead be cast as a bonus action. but you can still only cast 1 leveled spell per turn. so they can, say, cast magic missile at lvl 2, quickened into a bonus action, and then can use their action to cast a cantrip like firebolt. it is EXTREMELY common for new sorcerers to not understand that, and try to do something like, quicken a fireball, then use their action to cast another fireball. those are both lvl 3 spells, which isn't possible.
also, knowing the rules is obviously good, but what is better is knowing WHY the rules are there in the first place. drinking a potion is an action, rules as written. a LOT of dm's just make it so that drinking a potion is a bonus action, because it never feels good when you FINALLY get to take your turn in combat and all you do is drink a potion and then you have to wait another 20 minutes for it to be your turn again. that makes perfect sense. HOWEVER, the reason why drinking a potion is an action is because in 5e there is a significant reduction in a need for a healer in your party and potions are meant to be very easy to obtain and/or make. so think about how that might impact your party dynamic. but, this is also curse of strahd we're talking about and barovia is... pretty barren...
we have a rule at our table where if we get caught up in a ruling, if we can't find an official answer in less than 5 minutes, the dm just makes one. if you ever get stuck on a rule, google is your friend. and there's a twitter feed called "sage advice" that is run by the guys who made the rules. so just google "sage advice" followed by the spell or ability or whatever and you should get an answer real quick. that's also something to explain at session 0, that in order to keep things moving along, it's best that everyone knows their own abilities and spells PRIOR to gametime, and that you are setting a time limit for debating a rule to 5 minutes (or whatever you feel works) and that in the interest of keeping things moving if there's no resolution, you'll be making one. if there's an issue, make a note and talk about it AFTER THE GAME, NOT DURING.
that's something that has worked remarkably well for our table, but obviously you're free to follow that or not.