For moreinsanerer! What a good topic for a LARP day.
This is a really interesting thing to talk about because I've played a lot of characters that are very, very different, at least on the surface, but at their core (and in the way I play them) there are a handful of constant components.
As far as creating and developing characters, all of them tend to a) feel very strongly about something (even if it's "hail chaos"), and b) have something going on below surface level intended to be revealed over the course of game. I have apparently developed this reputation as Always Chaotic Evil (when I suggested I might be playing a good character last year people laughed at me), but statistically that's not quite true—it's just that whatever I have going on tends to antagonize someone, somehow, haha.
I think a lot of the characters I play tend to have some sort of strong interest in change/self-improvement particularly—even Kallie Sunshine, actually, whose motivation for trying to get half of game killed stemmed from wanting to erase a part of her life she didn't like and control her own narrative.
As for how I actually play my characters in game... I think I tend to be most interested in character- and emotion-driven storylines, because that's something that's a) always there and also b) fascinating to me. When I build characters who are good combatants I tend to also give them something along these lines because I find combat really boring most of the time. Bonus points for characters with strong feelings about family, because I have a lot of family feelings as a person. (Also, if I'm crying IRL in roleplaying it means it's definitely a good game. FEELINGSSSS)
It's like—haha I am really obvious in being a hella story gamer stan but as far as my fun is concerned "success" is having interesting things happen, not necessarily in completing investigation stuff or beating a bad guy. (That stuff's good too, though.) I think this has informed a lot of the way I like to run games; success should raise interesting questions, failure should create difficult choices, IMO. World of Darkness LARP doesn't always lend itself super well to this, but when success/failure is often a numbers game I think the interesting part is what it means to characters.
I've also become a lot more comfortable with just grabbing the Probable Bad Decision and running with it; I used to say no to things routinely in my first year of LARP that I know now were story hooks and the STs trying to give me cool stuff. There are some STs I'm a lot more cautious of a player with, because I know they love a "gotcha!", but most of the time my rule of thumb is Why Not Do the Thing, basically, if it seems like it'd be in character. (I think Kallie Sunshine helped with this. I basically had no reason to not do anything. My general roleplaying flowchart w/ her was "SURE WHY NOT", basically)
And, I mean, I still haven't managed to get myself killed in a game so I guess it works out pretty well for me? Though next year... next year it will be a goddamn miracle if I don't get killed in the first half, hahahaha. It's going to be exciting.