Space Between Stories has a quick and dirty guide to workshops:
Workshops are Not My Thing (I prefer to actually write larps), but there’s still useful stuff here to consider about pre-game briefings. There’s also some commentary about “heavy” settings and rulebooks, and their experience is that only half the players actually read them. Their solution is pre-game workshopping to establish a consensus setting and tone, but that can devolve into a lecture. But along the way they suggest a real solution:
The game’s advertising material should be enough to set player expectations and know what the genre of the game is
I’ve seen games which do this well. For example, Musketeers, described as “A swashbuckling larp of romance, espionage, and heroic adventure where fortune favours the bold”, set in “not-quite Paris 1625”. In two sentences, they’ve told you enough about setting and tone to know what its like and what sort of characters fit, without burying you in text. Its a really good job of setting expectations about setting.