This is a work in progress, mostly copied from an old email I dug up.
- If you can find someone to write the LARP with you, it will be immensely helpful. If you can find two people, that's even better. Even if the other people have no prior LARP-writing experience either. It will help if they like to write stuff.
- How many characters are you going to write? Smaller LARPs are easier to cast and may be quicker to write, but you may need to write them more carefully—a single dud character or plot can have much more impact. A large LARP may be more work, but it can absorb a lot more strain—it's easier to write in information redundancy, and extra things for characters to do.
- A modern or historical setting requires at least a bit of research to be realistic, and you should try to summarise it into a background for the players—but players can also research a real world era without you. Making up a background for a fantasy or science fiction setting frees you from a lot of the research burden, but if the setting exists only inside your own head you need to write down everything your players need to know—this can be incredibly time-consuming, and at least as much work as writing the actual characters.
- The playtest is your friend. Even (or especially) if you're writing a convention LARP at the very last minute, aim to have something runnable ready at least a week before—if anything crashes and burns, you'll be able to find out and fix it. There are experienced roleplayers who generally don't go to cons anymore, who will probably be happy to playtest the LARP. They will be able to give valuable input. If the LARP is small, you won't eat too much of the viable roleplaying pool.
- Think of a plausible reason for a bunch of people to get together in one place and talk a lot. There are a lot of story concepts which just don't work very well as LARPs because they don't involve people talking. If you have one of those, consider writing a module instead.
- Different plots in a LARP are story threads divided into parts and spread over multiple character sheets.
- Most of the LARP should be contained in the character sheets; there should be relatively little information that the DMs know which can't be reconstructed from the knowledge the characters have. Ideally, information in the LARP should emerge when people talk to each other and share their knowledge.
- Resist the temptation to put in giant plot twists and external events that none of the characters see coming. If there's something really cool that could happen to the characters, it will probably work better if some of the characters are the driving force behind it, and can do it to themselves or other people.
- Avoid including too much background information which is completely irrelevant to the storylines planned for the LARP, unless it serves a vital characterisation purpose. For example, don't include detailed references in someone's character sheet to an event that happened three years ago, unless it is either going to be important in the LARP (because other people also know something about it, and have some reason to bring it up), or it has shaped the character in an important way (made them claustrophobic, paranoid or mistrustful of lawyers, etc.).
- Each person in the LARP should be able to have fun and achieve things by talking to other people for several hours. They can also do a small number of other things with DM supervision, but talking is what really drives a LARP.
- No person's ability to achieve things and have fun should hinge on a particular specific event happening or not happening in the LARP.
- There should ideally not be a single possible pre-determined outcome for the LARP. The people present should have the opportunity to affect what actually happens.
- Avoid introducing huge paradigm shifts, or twists which largely negate important things people have been working towards during the LARP. It isn't much fun to find out near the end of a LARP that the complicated business deal you've almost concluded has ceased to matter because your business partner is actually Cthulhu, he is about to eat everybody, and everyone except you is an alien/cultist/wizard with a secret magical power. (There are actually several LARPs that do this; they tend to be annoying for the people not involved in those subplots.)
- Each person should have many possible things to do in the LARP. As many as five or six possible "goals" are good. They may not get to achieve all of these, and they may not even know about all of them from the start, but the important thing is that each player should be busy with things throughout the LARP.
- Think about the way that information is going to flow between different characters. Characters should need to talk to other characters, not only to get pieces of information they already know they need to get, but to get involved in new subplots and storylines. As the LARP progresses, players should become aware of new subplots that they can become involved in. Completion of the goals the players walk into the LARP with should lead to more goals, and more things for them to do.
- For example, a character might know that he needs to speak to his criminal contact and get some drugs from him. Upon speaking to him, he will find out that the drugs have been stolen, and some other person in the room might know something about that. Speaking to that person may reveal something else that the character was previously unaware of, but should be interested in—and so on.
- LARPs can be quite structured, with each character entering the LARP aware of the purpose of the meeting which is going to occur, and with a "checklist" of goals that they want to achieve. LARPs can also be more freeform—involving an unexpected meeting, and no pre-determined goals or anyone. In a more freeform LARP, it is still important to ensure that characters can find things to do once they get there.
- A LARP should contain at least some characters who are friendly and outgoing, and will actively want to talk to lots of people. If everyone is sneaky and secretive, and nobody trusts, likes or talks to anyone else, the LARP won't go anywhere.
- What is the first thing each character is going to want to do in the LARP? There should be at least one easy option for getting into things, like greeting an old friend, welcoming guests, giving someone a present, making first contact with a suspected ally, etc..
- Think about how the LARP can be wrapped up, and come to some kind of natural end. Why are the people there? What needs to happen for them to leave?