I'm a Google engineering exec who has conducted over 1,000 interviews. Here are the 4 mistakes I've seen even the best candidates make.

• Daniel Rizea is a director of engineering at Google.
• He says most candidates make similar mistakes regardless of tenure or experience.
• Being tired and not preparing for behavioral questions are two mistakes Rizea sees often.

I am a director of engineering in one of the biggest European wearable offices of Google. Throughout my career, I have conducted over 1,000 interviews and participated in hiring committees and hiring boards.

I've interviewed candidates with different backgrounds and levels of seniority, from product managers to engineers, managers of managers, and UX designers.

Regardless of function or tenure, most candidates make similar mistakes that cost them getting the job. Even the brightest candidates can fall in this trap.

Here's an overview of the four most common ones.

1. Thinking you're prepared because you're good at your job

The first mistake is what I call the 'halo of knowledge' trap. It happens when candidates are good at their current job and think that they'll also do great at the interview. This creates a false sense that they're prepared. The trap here is that the things required to pass an interview may be very different from what they're doing in their day-to-day job.

When was the last time any software engineer implemented a difficult algo (like red-black trees) in order to solve a work-related problem? The odds are very unlikely, but candidates are expected to be able to juggle with the theory in an interview setting.

You may have to code the solution to a given problem on a piece of paper or design systems on the fly while debating pros and cons. Coding the solution on a whiteboard or in an online shared doc is very different from what most engineers are used to doing in their day-to-day work.

Successful interviewing is a skill. If you haven't been interviewing lately, you will most likely not be good at it regardless of seniority or experience.

The only way to overcome this is to practice and recall the theory:

• Try to solve interview questions on your own, and talk out loud through the solution.

• Write code in an online doc or a piece of paper in order to get used to the same setup that will be during the interview. The more algorithmic and coding questions you do, the more you will understand to classify them in buckets. Practicing will give you a frame of how to think about them. You will learn how to identify complexity and make certain solutions more efficient.

• Do mock interviews. If you can find a friend who is an active interviewer that is even better. Some companies even offer free mock interviews for their candidates to better prepare them.

Coming out of university, I had a friend who wanted to land a good-paying job at one of the big tech players. Because he read books on interviewing and practiced dozens of times, he could take it to the next level and connect and joke with the interviewers. It became easy for him.

He ended up getting seven offers out of eight companies, who were all competing for him. He told me there were no shortcuts and that his success was based on a lot of practice and reverse engineering the process.

2. Being tired

Most candidates overestimate their performance in future interviews and ignore small things that can help them. One of them is making sure you are well-rested before an interview.

You will experience a sudden drop in IQ during interviews because they're stressful. I have seen many candidates scheduling interviews after a long day of work or at the end of the work week. During the interview, they weren't lacking knowledge, but it was clear to me that they were tired. They'd respond slower to hints (if they'd respond at all) and wouldn't understand my questions or would go on talking about some other irrelevant thing.

I confess, I've made this mistake myself and was disappointed in how slow I was. I scheduled an interview after a 10-hour workday. I got a dynamic programming question, and I couldn't articulate the solution during the interview because my brain actually froze. It was only at the end of the interview that I managed to find a solution when the stress went away.

You'll be doing yourself a huge disservice if you schedule your interviews when you aren't in your top form. Try to bump the interview to a day when you won't be tired. Your interviewer won't be as annoyed as you think — and more importantly, you'll be sharper and in a good mood, and do better overall.

3. Not picking up on hints and going down rabbit holes

During interviews, there may be moments when you get stuck. Most interviewers will give you hints — additional pieces of information that should steer you on the right path — but if you aren't getting them, you could ask.

From my experience, candidates can easily go down rabbit holes that don't lead to a solution or help the interviewers correctly assess them. A good way to avoid this is to pause and ask the interviewers if this is what they're looking for or if they're looking for something else.

When in doubt or when you get some hints that contradict what you are doing, ask your interviewer what they're expecting. I usually set clear expectations with candidates before the interview starts. I will interrupt candidates abruptly if I see them going down a path I don't want. This is in their best interest because I give them more time to demonstrate specific skills.

Don't abuse asking for hints. It depends on seniority, and some hints are ok, but if you need too many you won't be qualified as having actually solved the question.

4. Not preparing for behavioral questions

Most candidates are terrified about behavioral or soft skills interviews. Think about it: Algorithmic and data structures are more objective; you'll know if you solved it the right way or not. But behavioral questions are more subjective, and it's harder to know if you said the right things during a behavioral interview.

The good news is that these questions can also be approached analytically. Behavioral questions validate culture fit with a company's values and the organization. That's it! If you can start from here, you can work backwards.

Look up the company's values on the website or ask the recruiter. Most likely you will get questions that will show if you are exhibiting these values or not in your previous roles.

For behavioral questions, interviewers expect answers along this format:

• What happened?

• What did you do?

• What was the outcome?

Let's say a company considers teamwork one of its core values. Think about examples from your past roles when you went above and beyond to help one of your teammates to be successful or when the team was better off due to your actions.

Think about what happened, what you did and what was the outcome: maybe the project was successfully done and a new friendship started. Examples like this will show that you are already exhibiting these values and that you will be a culture fit with the new company.

Don't try to make things up, though. Chances are, if you're not a professional actor, interviewers will catch that you are lying and you'll fail the interview.

It's better to admit that you weren't in a situation the interviewer described and get another question from them. You could also say that you haven't been in a similar situation, but you can say how you think you'd approach it.

I've put my advice to the test

I experimented with this advice myself. I involuntarily did an A/B test with two interviews that I had.

For one of them, I didn't prepare at all and scheduled the discussion at the end of my work day. For the other one, I invested around 15 hours in recalling all the algorithms, complexities, technical architectures, and best practices so I have them fresh in my mind. I also did some whiteboard exercises and practiced writing code on a piece of paper. I looked at the job description of the company and tried to guess some of the challenges they are facing (growth, technology, organizational complexity) and their needs from somebody in the advertised role. I tried to find examples in my past experience where I was successful in navigating those challenges.

Guess what the output was between the two? It was orders of magnitude different. From "When can you start? Let's get you to meet the founders ASAP," to an immediate boilerplate rejection. I was the same person, but had made different investments when preparing for the interview.

Like most things, the outcome of an interview is mostly based on the effort that you put in

If you ask candidates why they fell into these obvious traps, most would agree that it was an oversight on their part. From what I've seen, some months pass and they will make the same mistakes in the future.

The best thing that you can do is prepare for it. Don't forget that interviewing is a skill. It's worth investing some hours in practicing and preparing for the job you desire and where you will spend the next years of your career. It will certainly be a very good return on your investment.

Disclaimer: The views presented are my own and can't be attributed to any past and current employers.

Daniel Rizea is a director of engineering at Google who writes about management and leadership in tech. He is a technology enthusiast and former startup founder.