It does not matter how great your credentials and references are- bad body language can kill any chance of you ever landing that dream job! If your interviewer cannot imagine you as someone who would be able to represent the company, chances are they will never hire you. They may even begin to question some of the positions you have previously held!
To impress your interviewer, aesthetics is everything. You want to show that you are confident and interested in the position at hand. Slouching, either while you are standing or sitting, can show the interviewer that you lack interest, are unsure of yourself, came unprepared to your interview, or even lack the work ethic that they require for the job. Sit up straight with your head held high above you shoulder. What this shows to your interviewer is not only are you confident, but you are also alert and are ready to handle any situation that they are willing to throw at you.
Having good posture also means that you are not fidgeting or leaning towards the door. This will cause your interviewer to feel as if you are uncomfortable about something. Not only is this a sign of nervousness, but also you can cause the interviewer to feel as if you are ready to leave the interview at any moment in a panic. If your interviewer does not feel that you want to be there, chances are they are not going to take your interview seriously and just give you a courtesy interview for just showing up.
You must also give your interviewer a firm handshake so that they feel that you have a strong enough of a personality to perform in any job. If your handshake is too limp, you risk the chance of causing your interview to feel as if you are unsure about something, or lack the self confidence to be able to make any viable contributions to their organization.
Maintain eye contact, and address the person that is questioning you during your interview. Not only is not looking your interview seen as rude, but it is also a showing of a lack of self-confidence as if you are hiding something. Talking to your interview and staring into empty space can also show that you are bored, or maybe that you are even lying about what you are saying.
Keep your body language in check- crossed arms can say you are closed off to new ideas. Hands on hips can mean defiance and leaning over into the interviewers personal space can make you come off as controversial.
Communication skills are important and body language is just another way we communicate. Having great body language can make or break any interview. If you think you are lacking in these areas it would not be a bad idea to practice in a mirror so that you would be able to critique yourself more thoroughly. In this economy, why let any job pass you by because of something as simple of having too limp of a hand shake.