Start a LARP. Seriously, it's easy and fast to do so. Check out other articles in the series if you don't believe me. Today I'll be talking about format your LARP might take.
Basically, in the world of LARP there are two basic types of events: campaign events and one-shots. As you go from one larp scene to another, you'll see one type being more popular than another. Majority of Croatian LARPs are campaign events, though there are a few one-shots here, most widely played one being Love is blue. If you haven't larped before, you might have already imagined LARP as one of those two types.
The difference is in format, purpose and how they affect players. Campaign events seem to be more popular for fantasy LARPs (though not in every scene), and they allow playing the same characters in future events, creating more opportunities for characters to grow. They are also very cost-effective, as they allow players to build up their gear over time - which is very good for fantasy and other genres which can have heavy costuming as it will - over time, players will improve their costuming standards, quite often over what they'll do for one-shot LARPs.
One-shots are usually time-limited. The game environment and characters within them will exist only once - although the event itself might be repeated, and the same scenario unfolded again with different (or sometimes even the same) players.
Differences between those two formats are much greater than "one continues, other does not". Campaign events can commonly lead to greater associacion and attachment between players and characters. They can also lead to very complex characters, with years of defining events behind them. They commonly reward players who've been around for longer with powers or other game mechanics, and can use the same stuff to keep players coming. They can also be showcases for the best larp gear around. On the other hand, campaign LARPs can go stale over time, and they can require more effort to make the entire setting more consistent and believable between events. Having (commonly) more game mechanics might lead to more powerplay.
For players in one-shot events, their characters won't exist past this one game. It's also easier to create a good story and concept for a one-shot game than for every iteration of a campaign LARP. These two can combine to form a powerful and immersive experience, akin to best moments of a campaign LARP, and players might engage in deeper roleplay, playing their characters to get maximum experience, without any out-of-character need to preserve them for future events. On the other hand, characters have very limited time to grow or change. And with every event being self-contained, event quality is even more crucial for attracting and retaining people, without the "leveling" mechanic to fall back to as a crutch.
Apart from being one-shot or campaign, larps differ in their length. In Croatia, the longest events are four days (Jaska and Crolarp, which are campaign style), while the shortest one was only one hour in length (Love is blue, one-shot). Worldwide there are plenty of longer events, and certainly some shorter ones. One-shots are typically shorter, but that's not always the case - e.g. Croatia's Maksimir LARPs are campaign style, but few hours in length.
Of course, there are plenty of exceptions to what is written here. The most high-budget larp ever made was Dragonbane, a week-long fantasy one-shot larp organized in Sweden in 2006, with over half a milion Euro budget, and a living, talking, fire-breathing, 26 meter long dragon... And a full medieval village built just for the event.
You're not expected to do something like that. It's something that's not only incredible for everyone who's already into larp, but also a feat that has never been repeated since... That event took 2 years to prepare. You're not expected to duplicate it, you can freely start low on budget, even with no money at all. But, something like that is possible.
Biggest LARPs by the number of players are usually fantasy, campaign style and several days long, though others might provide other benefits. There are really no wrong answers concerning style. It's just that... a style. Nothing more, nothing less. It might feel different or produce different effects, but all of it is "valid" LARP. There are even mixed types of events, such as a campaign larp that stops when its story arc is complete, or an event of several hours divided into periods which are at different times in-character. And you can start your own LARP in any way mentioned here, or think of something new. There are no wrong answers, and while there's certainly a lot of ways to do it, and a world of detail you can explore, the basics are easy. Start a LARP.