There are many tricks that will help you remember, but most of them boil down to two things: Focus on the important stuff and write things down. That being said, here are a few more detailed pieces of advice that might help you.
1: Get rid of clutter
I don't know anything about the Death House, but it seems to be a large mansion with a lot of rooms. The first thing you should do when tackling something like this is to get rid of the unimportant and uninteresting bits. Instead of saying something like "What door do you open? Second to the right, OK. It's a bedroom with these items in it. What door do you open next?" you should try to streamline your narrative. The players want to have fun and do exciting stuff, but while clicking on every little thing can be fun in an adventure video game, that kind of behaviour doesn't translate well into the realm of roleplaying. The not-overly-impressed player even said it plainly.
Instead, try using this approach: "You search the rooms as you make your way down the dark hallway. Some doors are creaky and hard to open, a few are locked. The rooms are what you'd expect in a house like this, a few bedrooms and closets, a small smoking room and a couple of completely empty rooms. You end up in front of what seems to be just another door to just another room. Who opens the door?" Instant drama and excitement, without having to search through a bunch of red herrings. This makes it a lot easier for you to manage your session since you only need to keep track of the important stuff.
2: Review the important stuff
If you run a published adventure, make sure to read it before you run it and make sure to pay extra attention to the important stuff. If you find there are a lot of small things scattered about that have to fall in place for the adventure to work, try grouping some of them together in the same room so that you have less to focus on and worry about.
As for any and all flavour text, just wing it. If a certain room has an eerie breeze that is just there to discomfort the players, don't sweat it if you add that detail to another room or omit it completely. Add your own flavour.
3: Make a list
I often write something like this:
- Kitchen: Ordinary kitchen. The herbs needed for the spell hang on a wall.
- Larder: Mostly has ordinary food, but could have a few potions if the party needs them.
- Master Bedroom: Luxury and decadence. There is a small pouch of money on a dresser and many unique statues in various places. On the floor there is a large casting circle with lit candles (See chapter 3).
I would not write out an empty cupboard or any other room that has nothing interesting in it.
4: Make a map
A simple map or floorplan can make it a lot easier to be consistent in your narrative.
Give each room a number and keep the details on a separate paper, but add the important things directly to the map. At a glance you can see where the players might find the staff or the herbs.
5: Constantly write stuff down
If you improvise the contents of a room, jot down a few words about the room on your list or your map. This adds consistency and makes it easy to remember things you've just winged into existance. This method can be used to improvise an entire building if needed.
6: Don't bother
A simple advice that works well with locations that are mystical in nature. If you accidently change the details of a room or location between visits, make it a part of the setting. "Hey, where's the doll you said was here earlier?" "Hmm, you can't see it in here. Maybe you just imagined it being here?"
Right, here's some rough advice for you, most general to least. Let's start with the most important:
Never be ashamed of doing your job.
Every storytelling game has a "facilitator" role in it somewhere, often times just assumed in GMless games to be something the owner picks up alongside being a player. Someone takes charge of the rules, teaches the game, and keeps it moving. As you might have read later on in Good Society, the role can be spread out among the players as they get more familiar with the game, but for now? It's on you to do what you can to get everybody else to participate in and create the story, and it isn't somehow a failure of teaching on your part that you need to poke and prod to get things going.
I mean, even boardgames aren't really taught just in the rules explanation. It's important to understand the limits of what you can do, but the game is in the playing of it, and actually playing a game is as important a part of learning it as, well, learning it, to the point that the first play session can teach more about the game than any amount of reading the rules.
You are playing not only the setting, the pressures and judgments and incidental characters of Regency England, but also to some extent the editor, pulling out character motivations, prying out sketches of backstory, looking for interesting bits. The Facilitator chapter outlines your responsibilities and provides some sample questions, but it doesn't really point out the secret sauce it's using in them, which can definitely help get a scene going.
How to Ask Charged Questions
So lemme pair up some of these sample questions with worse versions of the same:
How does your family prepare for the party? --vs-- What is your family doing?
Does the carriage make it before the storm? --vs-- When does the carraige arrive?
Did you know her before she left for London? --vs-- Do you know her?
Sample questions on the left, if it wasn't clear. Let me expand them and it'll be clear what they're doing.
Your family is preparing for the party. What are they doing?
There's going to be a tremendous storm tonight just after dark, lightning, rain, and mud. When does the carriage arrive?
And here's Dame Madsen, back in the country after six years in London. Did you know her before?
These questions aren't open-ended, asking after anything. They present some fact of the setting and ask for a character's answer, either as an interesting explanation or a dramatic or productive response. More importantly, they give a player something specific to think about, to orient themselves. More importantly for you, they let you present a character with some fact of the setting that will be dramatic to think about.
Charged questions aren't always necessary; sometimes your players will already be charged, because of ideas they brought to the table or which were raised in the scene. But even in that case, after they volunteer a course of action, it's best to restate it for the entire table - and that's going to sound a whole lot like a charged question.
Be Aware of Character Drama
I'm assuming you're playing with inner conflicts off for your first go at things? Less to think about that way? I won't be talking about them in any case, because there's already a lot you should be keeping track of as the editor. Unfortunately there's no master GM sheet to do this, so you'll need to press a humble notepad into service, with or without capital N. You need to know:
- character names
- character relationships to each other
- current character desires
- the features of the character role that should appear in the story (The [role] is...)
- the tensions in the character's family background that affect their reputation, both the common tensions of desire vs. morality and desire vs. societal convention, and the other one specific to family background
- character connections, a brief summary of each, and who's playing them
And there's more to write down than this. Interesting responses to questions that you want to keep in mind for later, incidental characters or places you introduce that could wind up being important later, all sorts of stuff.
I'm not saying you should expect to stop and flip pages every other sentence - just the act of writing them down for yourself should help keep them bubbling at the top of your mind. But when things seem stuck, look between your list of sample questions and all the things the plot says the character should be interested in, and you should be able to find something to introduce to keep going. As long as you're not destructive about your introductions you don't even need to spend resolve to do them!
But, okay, a game is a thing that involves multiple people. What to talk about with anyone else? Well...
Have you shared the Beginner's Guide?
The one that came with the game, not the Source engine meditation on the relationship between author and game by Davey Wreden. It's a different kind of game, something some of them haven't played before, so there's no shame in looking through a beginner's guide.
Though hey, come to speak of it, one of the most important elements of the Beginner's Guide (the Good Society one) is how it talks about the relationship between author and game. For purposes of having a good game, everyone is an author trying to write a good story, and if the story is satisfying and dramatic and touching and holds together, then everyone wins the game. So all the cards down in front of you that say your clergy socialite wants to manipulate two couples into being married without being found out and while helping any lost souls they happen across? That's not what wins you the game. In a sense, they barely even matter, except as they're there to provide things that your character is trying to frame scenes and spend resolve tokens to make happen in the story.
So if people are worried about seeing their character's reputation tarnished or their character's desire foiled, well, they shouldn't be. No one's trying to do it on purpose. It'll happen, or not happen, as makes for a good story.
Sacrifice by example, if you can.
I hope the setup has left you as facilitator with room to play a few connections, or even to pick up a main character. Because if it hasn't, it means you're trying to run this thing with the maximum of 5, and these kinds of heavy-involvement games get exponentially more difficult to manage as you add more players.
If you have connections, use them to prod their original players towards their notional desires, possibly in a way that brushes up against questions of reputation. If you have a main character, facetank all the bad things that can happen with a smile. See your desires foiled, let your reputation plummet, accept all the resolve anyone wants to offer you for throwing complications into your own life.
Perhaps, play for lower stakes.
If you can't play connections or a main character, or in addition to doing that, you might want to twist the game's dials off the default settings Collaboration puts you on and play it as a farce with no hidden info. (Though perhaps this is just my own also-fandom of Jeeves and Wooster talking.) Everyone is ridiculous, everyone's desire is known so everyone else can toss knives at it, and the entire point is just to shamble from disaster to glorious disaster. Mind the X-Card while this is happening all the same, but it can be easier to accept characters taking risks and failing grandly when that's what expectation is from the get-go.
Best Answer
Yes, it's fine to make it up as you go along.
Whether or not that works for you depends upon your ability to remain consistent and to improvise on the fly, but many a good campaign starts with nought more than 4-6 PC's and a map.
Also note: many a campaign lies stillborn, suffocated by excess GM prepwork. Many more get off the ground, then grind to a halt under the GM's reams of prepped details.
Too much is worse than too little.