Apocalypse World has lots of elements that kick in between sessions or have long-term impact only, and so aren't very fun in a one-shot game. What rules, character roles and mechanics should I modify or omit to make a single-session experience (with 3-5 hours of gameplay) work better?
Apocalypse World is one of my go-to games for one-shots, and I find that it shows off well in a single 3-hour (preferably slightly more) session, even without changing too much. This includes not using pre-made characters, because I believe the setup to be an integral part of the AW experience.
There are some ideas on it on the “Barf Forth Apocalyptica” forums, for example in http://apocalypse-world.com/forums/index.php?topic=490.msg4476#msg4476.
Do prep, filter playbooks and speed up character creation.
My concept for a one-shot is usually as follows.
- Break the rules and actually do some prep before session one. Come up with a front and a “colour”, a shape of the world, to bring to the table. I feel free to drop them if players come up with something cool on the spot, but they give me a situation to jump into immediately otherwise. My core prep are two rough types of NPC, a slaver and a family, that have interests and skills relevant to each other and will both come in contact with the PCs.
- Hand playbooks out according to “Who is the leader? What are you the leader of?” (and hand out a Chopper, Hardholder or Maestro, or something else if they have a clear picture and I have something fitting at hand) and “Who is the thorn in your side? Why?” (Hocus is a good one to try to sell here, if no-one jumps on it, then Brainer, Battlebabe and Faceless are good) to set a basic idea, sketch a setting, and then hand out other playbooks. For those I like Hocus, Brainer, Driver if the boss is a Chopper, and Ruin Runner, and if someone asks in that direction Savyhead and Angel.
- At character creation, make sure that people pick a name, a look and the special stuff on the back of the sheet so they have a good idea of their characters and can introduce themselves for Hx. Then do Hx and take it slowly (or use 2E! Simplifying Hx is a very good change that will come with it), making sure everyone gets a good image of the connections. The rest of character generation can be done later whenever convenient.
- Make sure to use the beginning-of-the-session moves, don't worry about the end-of-the-session moves only showing up once.
- I have played at conventions, where in other games people could buy rerolls for the benefit of some charity. In my AW games, I allowed players to buy additional D6s. Each such dice could be rolled and added to a roll (even after the roll), and each buy allowed them to advance one basic move, so that they could see the cool 12+ results in play.
The notes here, in particular the playbooks, are concerned with the first edition – I have only played one 2E playtest so far.
On Love Letters
You can find a basic treatment of the topic in the "Catching Up/Setting Up" segment of the book, p.273 1st ed/p.275 2nd ed, though you'll want to look at the 1st ed book if you can because it then goes on to detail a couple of scenario setup documents. They're missing from 2nd ed, probably for page count, because they're just extensions of things they're already teaching you how to do.
So here's the basic setup.
Step 1: Provide the necessary background.
A one-shot can effectively be thought of as a mid-season episode. The first session has already been run, people have spelled out the common threats and the MC has put them together into a map, and there are varying degrees of active dangers to the characters' lives, well-being, comforts, etc.
So provide the facts of the situation - where are you, what do you eat, what's the single biggest threat - and detail the responsibilities of whatever role it is people are taking on, as in @Anaphory's answer.
Step 2: Think about good and bad things.
Most moves let you pick from a list of good things you want to get, or a list of bad things you don't want to happen, and the higher you roll, the more good things you get to pick or the fewer bad things you have to pick.
Love letters aren't any different, but because they're intended to only be used once, you can have a longer list. Still best to keep it to around five or so, though.
Every benefit you want to offer people, or every threat you want them to dodge, also serves a secondary purpose, in that it communicates to people the kind of things their role has to worry about. So even if the hardholder doesn't pick to have their rule endangered by a lieutenant who's trying to make peace with the biggest threat, that still puts the idea in their heads that someone could be out there trying.
Step 3: Define the outcomes.
Once you've nailed down your list of things (which can be a mix of good and bad, see Lafferty's list with the one about Scanner in the examples), pick a stat to roll, which should probably be a marquee stat for whatever playbook you're handing it to. (If multiple off-stat playbooks could pick it up, such as perhaps a Hocus, a Savvyhead, or a Chopper, who could each be an early warning system, feel free to leave the +STAT blank and tell the player what stat to write in afterward.)
Then do the standard - if you've got a list of good things, they can pick some but not all on a 10+ and fewer on a 7-9. If they're bad thing, they pick some on a 7-9 and fewer on a 10+. Think about if you want to offer some kind of bonus if they get a 12+. And also think about what happens on a 6-. You're going to want to define that in advance, because you don't want to be flailing around searching for answers after the first roll of the game. "All the bad things happen" is a popular one, or maybe "GM's choice, not yours". If you came up with a list of only good things, let them still pick one on a 6 but detail what the cost will be - maybe they owe somebody a debt or have to trade away an advantage they previously had.