Common mistakes when interviewing candidates (and how to avoid them)

The most common interview mistakes are four: improvising because you went in blind, talking more than the candidate, deciding on first impression, and comparing each person against a different yardstick. All four have the same antidote: come prepared, with a core set of questions that’s the same for everyone, and—better yet—with prior evidence about each candidate. That doesn’t eliminate bias, but it takes away the space where it decides most on its own.

Almost no one interviews badly on purpose. People interview badly out of habit and lack of time: between one meeting and the next, you walk into the room unprepared and do what you’ve always done. The problem is that those habits have costly consequences: hiring decisions you later can’t explain. It’s worth naming them so you can correct them.

Mistake 1: improvising because you went in blind

It’s the source of almost all the others. You arrive without having looked at anything about the candidate, so you ask everything just in case and end up deciding by feel. The conversation gets long, hard to compare, and very exposed to the impression of the moment.

How to avoid it: prepare a core set of questions before each interview and, if you can, come with prior evidence. Assessing before interviewing gives you comparable signals about the person, so the conversation no longer starts from scratch.

Mistake 2: talking more than the candidate

It happens more than it seems. The interviewer, excited or nervous, fills the time with their own voice: explains the job, tells anecdotes, gives opinions. They leave the room with their opinion confirmed and little new information about the candidate.

How to avoid it: remember what the interview is for. Ideally the candidate talks most of the time, with concrete examples, and you follow up. Prepare the questions and, above all, leave silence so they can answer them.

Mistake 3: deciding on first impression

You form an opinion in the first few minutes and use the rest of the interview to confirm it. It’s pure confirmation, and it shows: you stop listening to anything that contradicts your initial impression. This is where the halo effect and similarity bias come fully into play.

How to avoid it: there’s no magic button, but it helps to have a common standard for everyone, comparable prior evidence, and notes taken during the conversation, not after. This reduces the weight of the impression, though it doesn’t eliminate bias: the decision is still human. We go into this in how to reduce subjectivity in the interview.

Mistake 4: comparing against different yardsticks

If each candidate had a different interview, in the end you’re comparing impressions, not people. “I felt better about this one” isn’t a criterion you can defend to an internal client.

How to avoid it: define a core set of questions that’s the same for everyone and back it with prior assessment, which puts everyone on the same footing before the conversation. That way the differences reflect a criterion and not the chemistry of the day. The comparison between formats is covered in structured vs. unstructured interviews.

The common thread: preparation with evidence

If you look at the four mistakes, they all get defused by the same thing: no longer going in blind. Prior assessment doesn’t make the decision for you or replace the interview; it gives you a comparable base so you improvise less, listen more, and compare with criteria. The final decision is still the team’s, and it can carry biases, but it starts from firmer ground.

In summary

The four common mistakes—improvising, talking too much, deciding on impression, and comparing against different yardsticks—share an antidote: preparation with a common core of questions and prior evidence about each candidate. That helps keep subjectivity in check without pretending to eliminate bias, because the decision is still human. To put it into practice, check out how to prepare the interview with evidence or the product.