Classpecting is my favorite and most difficult part of designing fan kids/trolls.
Personally, I just go on vibes and my own theories alone. I don't rely too much on other people's theories or the established canon classpecting descriptions (especially these... eugh...). I typically take the history of the character and try and figure out what may best suit them.
But it's a bit of a doozy because even in canon, characters aren't ever linear; they change along with the story. And that is what I think is most difficult about classpecting.
Still, I'm curious to know how others go about it! Especially since I'm stuck on classpecting some characters for a project I'm working on. xP
P.S.: Sometimes I see people go about it the other way around. I wonder how that works?? Story wise I mean. 'Cause I prefer stories that have more leeway for change. Which goes double for HS because of it's fans' contributions.