How do you vet a hiking partner before a remote backcountry trip?

I've seen too many stories about people getting stuck with unprepared or unsafe partners on multi-day hikes. When you're miles from civilization, trust matters.

What questions do you ask or checks do you run before committing to a long trek with someone new? Do you look at their experience level, ask for references, or just rely on a quick coffee meetup? What red flags would make you cancel a trip?