When it comes to finding a job, you don’t want to show weakness. Confidence is a huge 
part of getting a job. So here is a list of things that you should start practicing before the interview to show confidence.
- Review and recite the things you’ve learned from bad experiences. Have a group project that crashed and burned? Work in an internship that you hated? Think about what you gained from the experience, such as dealing with conflict, group management, or learning how to meet deadlines under pressure. Before your interviewer asks about the experience, already have a positive answer about the task.
- Practice your responses to anticipated questions. Don’t be caught off guard by any question in an interview. Review this list from Forbes of the 50 most common interview questions or search on Glassdoor for the company you are interviewing with and see if other interviewees have posted the questions they were asked. You won’t always have an answer, but you should practice answers in advance to be most confident in your interview.
- Improve your eye contact. When people get nervous, they often start looking around. You won’t appear confident if you answer questions while looking at a wall. Have a conversation with a friend, and practice looking in his or her eyes. The eye contact you make in a normal, comfortable conversation with a friend is the same eye contact you should be making with your interviewer.
- Smile in stressful situations. A smile in an interview shows confidence, but it might be the first thing you forget if you’re nervous. Practice smiling while saying “hello” to a stranger on the sidewalk or introducing yourself to a professor. Get used to smiling.
- Don’t apologize for things that aren’t your fault. Don’t let people walk over you. If you are a not-so-uncommon person who apologizes for everything, stop. This tiny improvement will help you be even more confident.
Purdue CCO Blog 
I completely agree with #2 & 3 – Be prepared with answers to common questions, and make eye contact when delivering your answers in the interview.
I know a lot of people who worry about sounding too rehearsed if they practice answers in advance. The truth is you’ll be nervous during the interview, so you’ll still sound natural. But you’ll be more confident because you already have an answer prepared.
I hadn’t heard #5 before? Do you have any example of times when people apologize for things they shouldn’t have?
-Bob
Thanks for your comment, Bob. I actually see #5 all the time. In personal experience, I work with a few female interns who tend to apologize for everything, like closing a door too loudly, walking into an office not knowing there’s a meeting, and other innocuous things. Our supervisor always tells us not to apologize, because there’s nothing to apologize for. Taking the blame when there is no fault can make one look weak in a work setting.