There is one thing you must do before you interview. You need to interview. Not the actual interview, but a practice interview or mock interview. Nearly every college campus offers access to a Career Counselor who can take you through a mock interview. Sadly, fewer than 10 percent of all graduating students take advantage of mock interviews. And fully 90 percent end up stumbling through several interviews before they have any practical sense of how they are doing—because that is when the rejection letters start arriving. And those rejection letters offer you nothing in the way of constructive criticism toward future improvement other than pointing out to you in the starkest terms that you failed your interview.
The mock interview is more than just a chance to work out your interview jitters. It is an opportunity to practice your interviewing technique and answers in a live simulation. It is also a chance to hear constructive feedback from someone who can guide you toward improving your interviewing style and presentation.
Just one mock interview will result in a marked improvement in your interviewing skills. Why? For the same reason that a speech is not a speech while it is still on paper or just floating around in your head. It is not a speech until you give it verbally. The first time you give it in front of an audience (remember your first speech in Speech 101?), it will come out nothing like what you prepared. It is the same with interviewing. It is not enough to look at an interview question and say, "Yeah, I know the answer to that one." You need to practice your answer. Live. In front of someone else. This is not the time to talk to yourself in the mirror. Seek out a professional and practice. Ideally, have the session recorded. That way, you will have two opinions—the mock interviewer's and your own. Remember, you get a totally different perspective from listening to yourself saying something contemporaneously than you do from the "out-of-body experience" of watching yourself later on the recording. Just as your voice always sounds different in a recording, so do your answers. "Did I really say that?" Yes, you did. Aren't you glad the image is captured in a recording (which can later be erased), rather than in a potential employer's mind's eye? Yes, you are.
Go through at least one mock interview. For maximum effectiveness, review your responses and then go through a second mock interview. Even if you ace the second mock interview, it will be well worth it since it will give you confidence in your first real interview. It can be a painful experience, since you are likely not as ready as you think. The feedback you receive is intended as constructive criticism, so do not become defensive or make excuses. Simply take in the feedback and change your future interviewing for the better.