Vague Plea for Help

[Tedective]

I'm going to start a campaign that focuses more on roleplaying than combat, this is going to be my first real DMing experience and I don't want to do something stupid to ruin it.
The setting is Ravenloft, I want the atmosphere to be scary and dreadful.

I guess I want DMing tips and tricks, some methods that experienced DMs would know.

As well, I want to know what to avoid doing to keep the game interesting, things noob DMs do that I can avoid.

Any and all advice is helpful.

[Tedective]

I've noted that I shouldn't split hairs with the players, overextending the characters actions to put them in danger might be a bad idea.

[GameSpawn]

The biggest mistake I've personally noticed new DMs making is trying to hard to force the players to follow the plot the way they (the DM) expects them (the players) to do so. Recognize that your players will surprise you, and if you give your players agency (which you should), you probably won't know exactly what's going to happen a few sessions out.

I personally find that the best approach is to define your world in terms of what the NPCs are planning, what their goals are etc. This way, they can react logically to the PCs, which ultimately results in your PCs having more influence on the game world (do be careful, however, that you don't become so involved in the NPCs' plans that you care more about them than you do about the players; your players are always the most important part of the game).

EDIT: I guess I should note that the comment not noting what's going to happen a few sessions out depends on how fast you play, and what type of setting you're in. Obviously, some settings are much more linear than others, but the general principle of "your players will surprise you" still holds.

[Tedective]

The biggest mistake I've personally noticed new DMs making is trying too hard to force the players to follow the plot the way they (the DM) expects them (the players) to do so.

I've thought about that and decided to make a bunch of unique NPC's. (One of the characters is basically Sherlock Holmes, so this is a boon to his hyperanalytical personality.)
Something that concerns me on that matter though is, should I have NPCs' fates be sealed unless players interact with them? Or should I roll randomly to see how the world's story pans out?

Recognize that your players will surprise you, and if you give your players agency (which you should), you probably won't know exactly what's going to happen a few sessions out.

Could you elaborate on what agency is? Like, giving them a way to change the story more easily?

One thing about this that intrigues me is adding a butterfly effect to the first adventures of the party, like saving someone could lead to that someone murdering more important NPC's perhaps?

[Scarce]

As for making things scary, you want to capitalize on fear of the unknown. The elf NPC turns out to be a horrible construct under a veil of stolen skin, the good guys and bad guys are never clear, and the full story is never fully understood. People are not who they seem, and neither is the plot.

[GameSpawn]

I've thought about that and decided to make a bunch of unique NPC's. (One of the characters is basically Sherlock Holmes, so this is a boon to his hyperanalytical personality.)
Something that concerns me on that matter though is, should I have NPCs' fates be sealed unless players interact with them? Or should I roll randomly to see how the world's story pans out?

Unless the players interact with an NPC, that NPC's fate doesn't matter . Whether what occurs with them "off-stage" is determined randomly or by what you think makes for a good story is really up to you (by which I mean, neither option is inherently superior). That said, the more the players know about what is going on off-stage, the more I would recommend you use game mechanics to resolve the situation. In my experience, however, situations where the PCs know a large amount about what's going on off-stage are relatively rare.

Could you elaborate on what agency is? Like, giving them a way to change the story more easily?

Agency is roughly a character's ability to control how they affect the rest of the world. Put a different way, a character's actions should affect the world in a way that makes sense. It's fine if the character isn't able to kill the king because he's too well guarded; it's not fine if they kill the king and it has no effect on the game world (this is obviously an extreme example, but the point holds for smaller scale examples as well).

One thing about this that intrigues me is adding a butterfly effect to the first adventures of the party, like saving someone could lead to that someone murdering more important NPC's perhaps?

This can be very good if done well, but be careful. If you have too many cases of the players well-intentioned actions inadvertently causing more harm than good, they'll get frustrated very quickly (at least, most people will; exceptions exist, of course). Most people like running into that guy they saved again; very few people like finding out that the guy is actually a serial killer and they should have let him die. EDIT: Although, I should note, the number of people who will like this isn't 0. Know your players.

[Tedective]

As for making things scary, you want to capitalize on fear of the unknown.

At first I worried about implementing monsters as common NPC's, but realized that most of the monsters in Ravenloft are intelligent enough to not immediately gulp down anything with a pair of legs.

Another interesting thing about Ravenloft is that divination spells and effects don't work, and alignments are hidden in nearly every circumstance.

[Larkas]

I'm going to start a campaign that focuses more on roleplaying than combat, this is going to be my first real DMing experience and I don't want to do something stupid to ruin it.
The setting is Ravenloft, I want the atmosphere to be scary and dreadful.

I guess I want DMing tips and tricks, some methods that experienced DMs would know.

As well, I want to know what to avoid doing to keep the game interesting, things noob DMs do that I can avoid.

Any and all advice is helpful.

First of all, good luck! And welcome to the fray.

Regarding the requested advice, you want a scary and dreadful atmosphere. You're playing Ravenloft, so that's only right. But how to achieve that? Well, keep the tension up! Don't give the PCs everything they'll need upfront. Make them feel powerless! But don't crush their hope: there must always be a way to achieve what they want, it just might be very difficult. Just be careful to not hide stuff behind puzzles that may only make sense for you: this is one of the easiest ways to make an otherwise fun session a drag.

Finally, you might want to take a look at E6. It's a D&D variant that caps level, but not character, development at 6th level. This way, your players will never overpower anything through sheer force of arms ("How the heck are we supposed to defeat this Dark Lord???" "Well, certainly not through brute force."). Don't feel pressured to use it, though. This is your first time DMing, you might just want to use the stock game and see how things go, and that's fine too.

[Tedective]

Most people like running into that guy they saved again; very few people like finding out that the guy is actually a serial killer and they should have let him die. Although, I should note, the number of people who will like this isn't 0. Know your players.

I guess I'm trying to stress the players with hard choices to make and obvious choices misleading them.

Examples being:
Save the thief (who would be seen later, turning his life around) or let him die to cannibal goblins?
Save the panicking, useless, royal lady (who is afflicted with vampirism, or cursed, or a were[animal])?
Deliver the final blow to a defeated enemy, imprison them, or let them escape for promised reward?

Lots of skill checks will be needed to notice the small hints...

[GameSpawn]

I guess I'm trying to stress the players with hard choices to make and obvious choices misleading them.

Examples being:
Save the thief (who would be seen later, turning his life around) or let him die to cannibal goblins?
Save the panicking, useless, royal lady (who is afflicted with vampirism, or cursed, or a were[animal])?
Deliver the final blow to a defeated enemy, imprison them, or let them escape for promised reward?

Lots of skill checks will be needed to notice the small hints...

I'd consider all of those to be perfectly fine (if you do go with the second one, just make sure it's the exception, rather than the rule, when they save someone).

[Tedective]

First of all, good luck! And welcome to the fray.
You might want to take a look at E6. It's a D&D variant that caps level, but not character, development at 6th level.

I was thinking that if the players could beat the darklord, miniboss, or other word for BBEG, I could just scale it to be a more challenging fight, adding levels, special items, goons, or phases to the fight.

I believe that a higher level shouldn't mean easier fights, but rather more content pushed against them and more weight on their shoulders.

A challenging game is a fun game.

[Larkas]

I was thinking that if the players could beat the darklord, miniboss, or other word for BBEG, I could just scale it to be a more challenging fight, adding levels, special items, goons, or phases to the fight.

I believe that a higher level shouldn't mean easier fights, but rather more content pushed against them and more weight on their shoulders.

A challenging game is a fun game.

Alas, that's not how the game works, specially with full casters. But really, DON'T use E6 for now. It's better to play a unmodified game first so you can make an informed decision in the future.

[Tedective]

Alas, that's not how the game works, specially with full casters.

Yeah, I won't use E6, but wouldn't I fight casters with rogues/casters and fighters with fodderfighters?

Isn't there usually a hard counter to a misbehaving/overpowered character (that doesn't involve rocks falling?)

[Larkas]

Yeah, I won't use E6, but wouldn't I fight casters with rogues/casters and fighters with fodderfighters?

Isn't there usually a hard counter to a misbehaving/overpowered character (that doesn't involve rocks falling?)

There can be, but it usually involves making the other characters irrelevant. Remember, the PCs are in this together. If you put fodder + caster BBEG, one possible scenario is everyone focusing on the small guys first (and the caster PC overshadowing everyone) and then getting to the BBEG (and the fighters being unable to do anything). Another possible scenario is you unwittingly overdoing it, knocking out the caster PC and... How are the fighters going to take him down? Don't get me wrong, I'm not saying it will happen in your game. Actually, this usually won't happen. But it might. Just don't freak out if it does, it's part of being a DM.

[Tedective]

Remember, the PCs are in this together. If you put fodder + caster BBEG, one possible scenario is everyone focusing on the small guys first (and the caster PC overshadowing everyone) and then getting to the BBEG (and the fighters being unable to do anything). Another possible scenario is you unwittingly overdoing it, knocking out the caster PC and... How are the fighters going to take him down? Don't get me wrong, I'm not saying it will happen in your game. Actually, this usually won't happen. But it might. Just don't freak out if it does, it's part of being a DM.

The people I play with are hardcore powergamers, trying to be as good as possible at level 20 combat (Hence why I'm doing a roleplaying heavy game). Someone will always overshadow someone else, but usually everyone has focused into one specific way of killing that everyone has a major weakness that some other player has as a strength.

Just rambling here.

[Steel Mirror]

The best advice I can give for creating an atmospheric game with a specific feel is the following: Get your players to buy in.

That means being up-front with what you want the campaign to be like even before character creation even begins. If you want to get them excited about the prospect of an RP-heavy game that is a little different from what you have done together so far, make sure you are excited when you start talking about it! Tell them the kind of cool (or I suppose terrifying) books or movies or comics you will be drawing inspiration from to craft this world for them. Encourage them to share their favorite influences from the same genre. Be open to suggestions for themes or campaign features that they have for you. Get excited together.

If you get them excited, or at least cooperative, with establishing the type of game you want, then you have gotten 80% of the way there. It sounds like you have some other ideas for the specifics of running the game, which is great. You need that too. But if you can't get them to "buy in" to the campaign concept, it will be a constant uphill battle, and that gets tiring very quickly!

I wish you the best, Ravenloft is one of my favorites, but I've never actually been in a game that worked out. Have fun!