Interviewing well is a vital component of a successful career and an art that few master. Most people get nervous when they have to face a panel of experts--higher powers--who decide whether you have what it takes to acquire the job you desire.
Facing judgment day isn't easy. Most people try to act--take on roles and attributes that are foreign to who they truly are--and the results are disastrous. As a doctoral student in clinical psychology, I've been fortunate enough to average attending seven interviews each year for the past four years. While I certainly have areas for growth, being interviewed by elite psychologists and therapists--people trained to read and interpret human behavior--has taught me many valuable lessons that I'd like to share.
Here are 10 mistakes most people make when interviewing and how to avoid them:

1. Not putting enough time, energy, and effort into your preparation.

People who don't put effort into researching the company, their mission, and the type of people they hire often fail to get the job. I learned that how prepared I feel in terms of both answering questions about myself and knowing facts about the organization is directly correlated with my performance and level of comfort.
Spend the time you need to build confidence in yourself and increase your knowledge of the company.

2. Failing to maintain awareness of your posture and body language.

As a psychologist in training, I've grown to learn my tendencies: crossing my arms or leaning back when I'm anxious. Now I ensure that my body language is open, grounded, and non-defensive. That behavior shows others that I am comfortable, receptive, and confident, and has the added benefit of sending messages to my brain to remain calm.
Practice becoming more aware of your body and know your tendencies in stressful situations.

3. Talking too much.

Amateurs think that they need to cover every possible bullet point with the interviewer to appear competent. This anxious tendency often works against them, because the interviewer becomes more attuned to their anxiety than the content of their speech.
Silence can be powerful; learn how to pause and know when your answer is good enough.

4. Being afraid to revisit earlier questions and topics.

One thing that psychologists and most interviewers value is the ability to be self-reflective. This skill is correlated with emotional intelligence and conveys that you think about how you affect others. Sometimes it's absolutely appropriate to link your current answer to something you previously stated.
Practice noticing trends and patterns in your messages, and don't be afraid to revisit items--especially when it shows self-reflective skills.

5. Mumbling or rushing your speech instead of thinking first.

Nothing is worse than word vomiting or going mute--especially in group interviews. If you can't handle the pressure of an intense interview, how are you going to handle a chaotic day at work?
Tell your interviewer that you're going to take a second to contemplate your answer--it shows confidence and composure.

6. Not supporting your statements with evidence and examples.

Telling people about yourself and how you work is good, but showing them how and why you work the way you do is better. Give your interviewer a glimpse into what makes you tick by explaining your values and by providing real-life examples. It will make your claims more significant.
Explain the how and the why for each statement you make.

7. Underestimating how much your appearance matters.

Yes, it's a superficial world and you need to take that into account. For example, I'm aware that my beard conveys wisdom and masculinity, my purple shirt shows I'm connected to my femininity and creativity, my glasses say "Hey, I'm smart," and my mala bracelet shows that I'm grounded.
Everything on your body speaks to who you are, so think through the messages you're sending to others.

8. Not preparing meaningful questions to demonstrate competence and curiosity.

The biggest rookie failure of all time is not preparing questions to ask the interviewer. Don't be that person who ends an interview without asking questions that can further your credibility.
Instead, compile a list of questions that highlight your attention to detail and ability to critically dissect information.

9. Failing to explain your value and highlight how you and the company are a great fit.

You're basically trying to establish a romantic relationship with someone who is convinced that they don't need you. When you don't explain why you're a good fit, there's almost no chance that they'll accept your offer to go on a date.
Show what you can bring to the table and why this relationship will be mutually beneficial.

10. Allowing stress and anxiety to ruin your introduction and closing.

Stress and anxiety happen to the best of us, but you need to focus.
Do whatever it takes to find your groove before interviewing, and then be intentional about your first and last impression--make yourself stand out.