Ask HN: During a tech interview, what are some green flags and red flags?

There have been lots of recent posts about job search, but so far I haven't seen anything focused on interviews. I might have missed it, but a quick search didn't show anything.

What are some green flags and some red flags you look for during the interview process?

As interviewer, what do you usually look for in a candidate that help tip the balance to either a "yes" or a "no"? When you had several candidates to choose from at the end of the interview process, what helped you decide one over the other? Any tips for candidates that would help them get at least a screening call and not get ghosted?

As interviewee, what do you usually look for to try to ensure beforehand the job is a good fit? How do you usually prepare for interviews?

For those who already have a job, do you have any examples of things you wish you'd have asked during the interview before starting the job? Any things that looked or sounded "not so good" during the interview that turned out to be not that of a big deal? Things that looked or sounded "good" but turned out not that good after all?