Recruiting, like many managerial activities, is somewhere between an art and a science. Getting people in the door is a numbers game in a lot of ways (lots of emails, phone screens and second phone screens that don't work out). But the interview loop and determining whether or not to hire people is, in my experience so far, a lot more difficult. A few things stand out to me, though, as things you can do to improve your chances and build teams that work well together and execute at a high level.
I'm surprised by how many places don't do this. The pre and post-huddle are the most important 15-minute meetings you'll have once you decide to bring a candidate in for a loop. You get all the interviewers together and the hiring manager gives them context on the candidate, the role, the responsibilities and then assigns each interviewer an area to cover and answers any questions. A PM and Engineering Manager might be assigned to talk about working across disciplines and on deadline. Designers may tackle whiteboarding. An engineer may do a quick CSS exercise.
It's really important to give people specific things to talk about. I can't count the number of times, before we figured this out at Etsy, that we'd all wind up talking about the same thing to the candidate over and over and over. Boring for them, not informative for us. It's also critical that you establish some consistency - both in the areas covered and the questions being asked. If you do the same whiteboard exercise a dozen times, you have a lot of relative data to work with that will help you make more sophisticated, informed decisions.
Experiment with different groups of interviewers.
You're not looking for people who form a consensus or agree with you. You're looking for people who are engaged, empathic and invested in making the team better (and not just filling a role). The best post-interview huddles I've been a part of have centered around pros and cons, insightful observations of 1:1 behavior and why that person could work out for the team. It's incredibly easy to have one negative experience skew and derail an entire interview. A great group of interviewers knows that's a single datapoint, but is careful to list out the other points. They look for trends in addition to the areas they were assigned to investigate.
Over time, you'll find the folks that are great interviewers and you can begin relying on them to help you make solid decisions about who to hire. You can also lean on that group to help you train up other people to become strong interviewers through shadowing and mentorship.
Optimize for avoiding false positives.
At all costs. I can't stress this enough. I feel like people say "a maybe is a no" a lot, but you have to practice this. Brutally. But we have to hire someone now or we're screwed and this person could maaaybe work, you're thinking. No. You're way more screwed if you hire the wrong person. So much more screwed. Don't do it. Contract them or something if you're desperate. Endure the few false negatives (someone who's great, but you miss out on because you're cautious) to avoid the false positives.
The tough part is that, a lot of the time, it's not cut and dry. There have been plenty of times where I (or another design manager) felt like we were missing out on an opportunity by not hiring someone. But if you trust the people on your loop and the reaction is mixed (or generally negative), let that candidate go. Sure, maybe the loop got it wrong. Maybe things would have been totally fine (or amazing!) with that person working with you. But believe me, it's better to be wrong about someone great than to be wrong about someone toxic. Hiring the wrong person is costly to you as the manager, to the people they work with and to the organization...
Except sometimes you have to YOLO and override everyone.
At Etsy, we design managers wound up forming an unspoken agreement: if you were the hiring manager and the loop didn't pan out, but you felt over-my-dead-body-do-we-not-hire-this-person strongly about the candidate, we'd absolutely hear you out. We would all work together to determine what would be necessary to convince people that it was a good risk to take and go from there. Sometimes that was a (paid) design exercise, other times it was having the candidate meet with people a second time in a more casual setting, whatever we thought made the most sense based on the feedback.
The trick is that we weren't doing that very regularly, in fact I think we each played that card once in two years. It was incredibly rare, which made us all trust each other when it happened. And the crazy thing is, the person who fought for the candidate was proven right every time. The people we hired from those discussions turned out to be some of the most productive and awesome folks on the team. Which isn't surprising. We were initially optimizing against false positives, so the reconsideration wasn't so extreme. Additionally, when a manager is willing to fight hard for someone they want to hire, you can usually rest assured that the manager will put similar energy into supporting that person once they're in the organization.
Optimize your process.
Every time you go through a recruiting process, make sure to check in with yourself, the candidate and your team. What went well about that, what could be better, what happened that wasn't expected? Hone the process over time so that not only is the experience a solid one for candidates, but so you know you're reliably identifying great future coworkers, avoiding false positives and reducing the number of false negatives. A sophisticated and thoughtful recruiting process will set you apart as an organization and help you craft a world-class team.