After shadowing one of my colleagues' interviews, I was asked my opinion not of the candidate but rather how the interview itself had gone! After writing up my opinions on interviewing, it was pointed out that more people might be interested so I massaged the collection of ramblings into what is hopefully, a coherent article that someone new to interviewing or setting up interviewing processes can take something out of.
The original feedback happened pre-corona, but most of this still applies.
Before the interview
So you've seen the CV, you've read the resume, and now you're itching to interview. But wait! First comes the preparation. As they say in other industries, it's all about the three Ps - preparation, preparation, preparation (or was it practice?)
That being said, your preparation notes probably shouldn't make a physical appearance in the interview itself. I say probably because until you're more experienced they will likely be necessary, however you still shouldn't be facing the candidate over a looseleaf strewn, mad-scientistesque desk. Even if you need notes, you should be confident in the general structure of the interview, and how much time you want to spend on each part.
Something to remember is that an interview is technically public speaking - yes, the candidate is the one trying to impress, but they are also evaluating whether the company is a fit for them! The questions you ask, how you talk about your colleagues, and what you reveal about your company can have a lot of impact on whether the candidate accepts your offer.
When you know what you want to evaluatie in potential candidates it's time to create a standardised set of questions that all interviewers can ask. This way you know that everyone is looking for the same things, and it helps to not have to reinvent the wheel every interview.
Besides the obvious benefits, a list of questions that everyone asks also works to remove bias from the interview. Interviewers can't give candidates that they like "soft" or "easy" questions, and the answers that you get are easier to compare to the baseline examples of good and bad answers (did I mention the baseline answers? They're great, but require some experience to get a feel for the typical answers candidates give and what you find acceptable)
The set of questions should be specific for the role you're interviewing for - you wouldnt ask the same things of a backend developer as for a designer. And nor should you! Of course, every absolute has an exception - I've sometimes come into interviews prepared for one role and had it suddenly pivot to another role - having a list of questions to switch to saved my bacon in these situations.
Besides the role-specific questions, you should also prepare some questions that apply to all candidates. These sorts of questions tend towards evaluating if the candidate would be a general fit for your team or company. These include questions around why the candidate chose to interview with you, why they're leaving their current position, their general style of working and communication patterns.
When creating questions, take into account the resources required. Would the question benefit from a whiteboard? Could a graph make the answer clearer? If you're doing your interviews remotely (and you should be by now...) then you might want to reconsider these types of questions.
Interviews should always be conducted in twos - no more, no less. One to lead, and one to be the secondary.
Interviewing with a partner is another step to ensuring that you don't end up with a biased result - having another person to help evaluate answers and ask questions gives you a separate window into the candidate. I've had partners pick up completely different cues than what I did, but I've also had them give the exact same points that I had already noticed. In both cases it was valuable.
Another benefit is spreading knowledge - when introducing someone to interviewing for the first time I like to follow a standard template where they shadow a few interviews, co-lead a few, and then I take the backseat and shadow them for a few before setting them free to start the cycle anew.
That being said, in general I believe it's better to have one person "lead" the interview. They are responsible for asking most of the questions, but it's essential that they leave a beat between questions to let their partner jump in if they want to. This can be difficult to remember to do if you are excited about a candidate or if it is flowing well.
During the interview
Candidates are people too[citation required]. If you're having back-to-back interviews it's better to lose 5 minutes at the start of the interview, and gain a slightly fresher candidate who won't spend the time distracted by a full bladder or parched throat.
Maintaining flow with the candidate is good, but not blocking other interviewers is gooder. It's okay to end 5 minutes early if the candidate does not have questions, or even skip this portion entirely. Respect the candidates time - be early to the session so that you can start on time, and end the session on time - some candidates may have public transport to catch, other meetings, etc.
Interviewing is a stressful experience, and some handle it better than others - some people are completely relaxed in interviews, but some are totally freaked out. Thus I find it best to structure the interview so that it starts with something that the candidate will feel "safe" on - something that they have prepared. The way I do this is by first introducing myself and my fellow interviewer (we have the candidates CV, but they don't have ours, so it's only fair). After that I ask the candidate to give their 10,000 foot overview, which lets the candidate start the discussion and leads nicely into a discussion of their past projects and experience.
An interview should be like a river: flowing gently along paths of least resistance, while going past interesting landmarks along the way. You should know when an opportunity has been missed and press forward - they almost always come up again later. A great way to recognise if you're doing a branch-and-bound model is if you keep jumping backwards in the conversation to the same point to ask more questions. Another sign would be if you put down sign-posts to alert the candidate to points that you want to come back to.
If there are two topics that you want to ask about, for example handling friction within a team, or how they handle constantly changing project scopes. One option is to simply ask these questions directly. One after the other. Better would be to walk through a conversation with the candidate and lead them to where the questions naturally fit.
For example, one such path would bet taking a project they listed on their CV, and starting with asking them to describe it. Typically they will focus on their involvement in the project (its an interview after all). This is easy to lead into asking about how large the team was, to how it was working with teams outside their department, to how these teams influenced the project scope.
As part of the flow I prefer asking "how" questions, rather than "what/where/when" questions. Interviews are better as conversations and not just lists of facts. This is a skill that takes practice and interviews flow much better when you've done a lot of them.
In interviews sometimes you don't get the answer that you were expecting. Sometimes it's worse than that and you get an answer that is incredibly tone-deaf, off-base, or just plain wrong. It's best to not directly acknowledge an error, but rather make sure if you really understood what they meant. Here I like to use the Socratic method and ask pointed questions to better understand their answer.
Remember, the interview is not only about finding the best candidate, but about the candidate finding the best company. Don't rush in at the last second (or worse, late) moaning about whatever the latest frustration is - rather be cool, calm, and collected. You represent everyone else in the organisation in that moment, so also make sure that you embody your culture and company values.
Selling the company to the candidate is only one aspect - you should also be prepared to sell yourself as a potential coworker as well as the position itself. Thus you should understand what the position entails, and the level that you're looking for. It's of special importance to know what your job adverts say!
At the end of every interview it's important to flip the relationship and let the candidate ask their questions - almost every will have at least some questions. Sometimes the questions will be surprising, but after a while you'll notice some common questions that keep coming up so you should be prepared to answer them.
Besides the typical "what are the next steps" and "when will I know if I'm through to the next step?", a common question is "tell me what a day looks like in this role". You should always be honest when answering candidate questions, however it doesn't hurt to pick one of the better examples. Other classic questions include the best parts of working at the company, the type of coworker you're looking for, or even negative things like recent bad reviews on glassdoor or even the app store.
After the interview
If the candidate is going to be doing back-to-back interviews, then a quick alignment with the next interviewer can be useful. You have to be careful not to bias them, so stick to factual topics such as if there were any questions that you ran out of time (which you would like the next interviewer to ask if they have time), or any areas that were total red-flags which need to be re-asked (for example, if the candidate was fired from a previous position).
Write down your notes and feedback immediately, but don't submit it. You should avoid speaking to other people involved in the interview until your thoughts have been captured. Even saying that the interview went "okay" can really highlight a bad interview. By taking some time before finalizing your opinion you avoid any recency bias. This is often a good time to take a step back and prevent overselling a candidate.
When writing your feedback it's best practice to always refer to the person being interviewed as them/they/the candidate. This has several purposes, chiefly not allowing any gender bias from someone reading your notes. Another benefit is that it's always clear when a comment is about the candidate or about something your fellow interviewer asked or said.
If you're ever uncertain about a candidate, that is a strong indication that it's actually a "no" verdict. Would you be willing to have this person on your team? Reporting to you? Being your manager? We want to hire people that we are excited to work with, people who will immediately make the organisation better for having them, if there is any doubt then its best to not continue.
When delivering the decision I prefer to use a 4-scale, that leaves no room for ambiguity. At the bottom is the Hard No. This is reserved for candidates that you think would actively harm the organisation, to the point where you might not be comfortable continuing to work there if they were hired. The Soft No is the more frequently used - sometimes there are cases where the candidate might move forward in the process anyways (such as at a lower skill level or different role), but normally most are simply rejected. The Soft Yes indicates a positive outcome, where the Hard Yes is reserved for candidates where you are willing to go out of your way to actively advocate that they are hired. A Hard Yes is a rare thing, but feels incredibly satisfying when they're eventually hired.
To add to that, A "no" is a "no". We hired our coworkers - if we don't trust their opinion why are we asking for it? If they consistently say "no" then it should be evaluated if they continue performing interviews, but a single soft no should be evaluated if the concerns can be mitigated. Hard No's should always be instant rejections.
and finally... Don't forget to reflect on the process and keep improving it