-You are not always going to get fear. Some players are capable of genuine fear while gaming. Most aren't. If you can't, don't worry about it. Fear mode is nice, but there is also Argento Mode, with sudden discontinuities and mayhem and panic. I recently ended a session with a player gently escorting a screaming cop into a hotel suite where Jez was fondling the toothed bosom of the wolfmother, Cole was on a bed with 3 dead naked teenage boys and Mandy was rolling a 01 maximum impale to fire completely blind ("I'm not looking, I'm not looking") at the first lady and save the world. That would be Argento mode.
-Fear mode looks like that.
-Do try to get an emotion. Disgust is pretty easy. You don't necessarily get emotions by thinking up brand new ideas so much as by describing whatever idea is there in enough sensory detail that people are actually imagining it. Tactile detail is probably the best. Like ok, there's the old Cthulhu statue and then there's You run your hand across the surface and it feels like--Have you ever run your hand across someone's skin in the morning? Like that--only also stone, like unaccountably warm. And bulbous, like tumors emerging. Just one emotion all night is ok.
-If you have someone capable of fear: run the game and start with any emotion you can get. Attachment to an object, liking an NPC, pride in the PCs accomplishments, whatever. If the emotion is negative (disgust, etc.)--good. If it is positive, sour it--have the enemy ruin it, brush it aside: "Your machines, your knowledge, they will not save you, your hope is hopeless" Most negative emotions are adjacent to fear. Just push them until they are fear.
(-And, of course, if you have someone truly fragile: then stop. Don't be a dick.)
-A scary thing: the familiar or otherwise comfortable thing suddenly being alienated from you. Your friends don't know you, your dog has no eyes, the human is not acting human, etc.
-Another scary thing: the skin is part of our immune system. Our first and most visible barrier. It is The Horror Threshold. Things that get past the skin, are under the skin or push through it, disrupt it, these things are horrible. If you can make players think about The Body it'll get you into The Mind pretty quick.
-Design the adventure with at least 2 powerful images. Just think of two things that interest you and are compelling. One is the first intimations of the horror, one is The Final Horror. Something fucked. You're good.
-Don't knock yourself out with the Mythos. You look up some mythos thing and you know what it'll tell you? Lovecraft mentioned it in 4 separate lines in 4 separate stories and each time it was some whole other thing. You know what Lovecraft would do? Make up something totally fucked up. Just do that. Worry about whether it's Hastur or Nyarlathotep later.
-Funny is good. Funny is great. In fact, let yourself laugh. Like sometimes if you are GMing you want to not laugh because you've got this adventure to run here but seriously, you do not have to Be A Fan Of The PCs, but be a fan of their players, and their jokes...
-...and their anything else they do right. If there is a phrase or image or line they come up with that is just perfect, say that. Stop the whole game and say that. In general: when anything cool is produced by players, encourage it. This has two effects: encouraging the player and showing everybody that its ok to go ahead and act--this activity will be rewarded.
-Try to remember who is insane. This can be hard, especially when the full mayhem is running:
Me: "Alright, the man with the leech face leans in, putting his face completely around your face and trying to sort of kiss you"
Guy playing a character based on his alcoholic Native American healer uncle: "Well, I'm still hallucinating, so..."
Me: "Yeah, right, so you are looking into his gullet and you see you are looking down into the coils of the great snake from which all of the world emerged in the time of the kicking rabbit and the blood clot boy and..."
Guy: "Well then I'm going to try to get _further in there_ "
Me: "Ok, so you grab it by either side and push your face into its mouth..."
And to think I would've missed it had he not reminded me...
-Likewise: try to remember who is on fire.
-SAN checks for seeing monsters and what all are gonna happen, but remember to run SAN checks for just mundane badness like seeing dead bodies and accidentally shooting civilians and suchlike sundry minor devastating incidents. Lose a few here and there once in a while. If you look at the stats for like a Nightgaunt, you don't necessarily lose that much SAN for seeing one--but of it's built on a bed of disturbing events...
-Purity has its limits. No matter what, Lovecraft stories aren't about 4 people. Definitely not about 4 people who are too terribly interesting. You're already not going to recreate a Lovecraft story. Just go for something good and twisted.
-The basic Hunter/Hunted structure can be bolted to almost anything. Even in the middle of an adventure. If the PCs are not moving toward the Horror, have the Horror move PCward.
-Things that make Call of Cthulhu easier:
*One insane PC does the work of a wandering monster. Essentially, when a PC starts getting jittery, play on it, use it to your advantage, that PC is the show now. Squeeze as much adventure as you can out of that PC.
*Everything is normal except the stuff you added in. In fantasy and SF you get an Oskar Schindler thing going on Oh with a little more effort you could've put something weird there and there and there. In a horror set up you just need a normal world. Just describe it creepy.
*Supernatural horror is pervasive: psychic emanations or dream echoes or what-all can pretty much account for any weird thing happening in the vicinity of the Horror. You don't need too much of a reason to have something strange happen all of a sudden.
*Stats are easy: Monsters therefore can be thought of as having hit points of 1 or 2 or 3 times human or 10 or whatever. The monsters have some chance to hit the PCs (60%, 70%) and some damage they do when they hit. Describing them and making them horrible and keeping them around just long enough that fucked up shit has time to happen while the players are encountering them is the key. In general, monsters have lots of hit points and don't dodge because they are implacable. But whatever works, really. Unlike D&D monsters, they don't have to actually be that mechanically tough for players to register them as dangerous or that mechanically interesting for the players to register them as interesting. Because it's the only monster in the game and you have essentially spent the whole game making them feel dangerous and interesting.
-It helps to have at least one person who will roleplay-as-in-act at the table. This lets other people know its ok and will be fun and not superfluous. In our session Cole did a great job of being the cop who was like: Well, I understand you are an indigenous person and you got your, uh, native medicine understanding of this, uh, Humbawamaba kinda thing and all I know is there's like a baby goat coming out of this guy and if you're telling me it's some kinda spiritual thing I'm with you because I ain't never seen that before. And then everybody sees that that's fun when the player acts and it lets them know its ok to do that and then it goes.
-Build the goddamn adventure around the way the goddamn players act and react. Horror is, basically, about a person with a personality and then a Horror that personality faces. Ripley and the Xenomorph, Rosemary and the Baby, The Torrances and Jack, the anxious Lovecraft narrator guy and Cthulhu. Everything between them (the physical set up, the plot) is just there to help dramatize that conflict. If the players reactions are giving you so much there isn't time for some structural device the adventure-as-written gives you, that's ok. Just let that happen. So long as you fit something horrible in before everybody goes home, it's all good.
-You can skip the resistance table--just roll d10+stat vs d10+stat for any contest or somesuch. BRP is an extremely robust system. Probably the most robust yet devised, you can fuck around with it and bolt all kindsa shit onto it and it still won't break--at least for human-scale conflict.
-Horror games have 3 parts: the parts where your PC investigates, the parts where you--the player--are scared, and the parts where you act. If your party is incapable of fear then the second part in the middle is a kind of acting (acting scared). Give players a chance to do all these parts and go with whichever ones seem fun for that group. All have an ability to shape the adventure, let it.
-I like to start with a picture, like in yesterday's post. Gets the PCs right into the scene and gives them the feeling there is something concrete to investigate. The "here's a bunch of guys" or "here's the crime scene" photo gives you a lot of details without you having to describe each one and trying not to lampshade the right detail by drowning it in a series of irrelevant details. Also, if you don't feel like you'll have words to describe The Horror when it comes, you can try to find a picture of that.