I've interviewed hundreds of people over a long time across industries. Here's some heuristics I've learned:
Hire people curious about the work instead of the perks
Everyone asks about salary and perks and 'future prospects' in a job interview. But the best candidates I hired were those who got visibly excited about details of the work itself. They would almost forget that they were in an interview and were genuinely curious about the type of work they would be doing.
Hire people not afraid to pause and reflect
This one is subtle, but I've found that most candidates are very eager to answer questions as quickly as possible. Nothing wrong with that - they're under the searchlight and are trying to impress. But some have the confidence and self awareness to pause for a minute before answering a tricky question - even ask to be given a minute to collect their thoughts. These are usually good prospects.
Hire people with a lot of interests
I think this one is obvious, but easy to overlook. Of course job skills to match the work description are important. In general though, people with a wide range of interests and a healthy opinion about the state of the world tend to do better.
I'm constantly amazed at the candidates, specially fresh grads, who have glowing skills but not even aware of last week's headlines - that's always a bit of a red flag.
Hire good listeners
Everyone loves to talk, but few listen intently. In an interview, the candidate is supposed to do most of the talking - but are they also good listeners ? Are they paying attention to any followup questions or cues that you might be giving ? or are they so caught up in their own answers that they completely miss the point. Good listening is a valuable skill - watch for it.
Hire people you wouldn't mind having as a boss This one is a bit unusual, but sometimes it helps to do a mental inversion. Is the candidate coming across as a person you would be excited to work for ? If he or she was already in the company would you be excited to get on their team ?
Hire people unlike yourself
You are more likely to hire people who are more like you. You will find them familiar and relatable and likeable. But if you're trying to create a team you want diversity, you want people who think different from yourself, who would challenge and grow the scale of what you do. You don't want a lot of "mini-me's" on the team who always agree with you. Hire your opposites.
So there you have it. None of these are infallible, and none are standalone. As I said these are heuristics, but they can be a useful checklist of things to look out for. Happy Hiring !