Abraham Lincoln one of the most influential presidents of USA has said"If  I am given six hours to chop down trees , I would spend the first four hours sharpening the axe".This saying suggest how good preparation  is advantageous in one's life whether it is interview  or anything else. Your interview session may last for twenty minutes,thirty minutes or an hour, but you have to prepare yourself for much longer period. By preparing ahead of an ensuing interview, you have given yourself a distinct advantage. Many of the job seekers or admission seekers develop a belief that they are smart enough to handle the interview successfully and there is no need for specific preparation for an interview. However this belief turns out to be fallacious and they do not fair well in the interview as they should have done. This happens not because of their lack of competence but because of lack of their mental framework in the interview process.
Therefore, there is a need for specific preparation for an interview.  This preparation will help you in two ways .First you will never feel surprised or awkwardness even if you face any unexpected questions from the interviewer. Second when you have prepared yourself fully, you develop confidence in you. Because of this confidence, you can do much better than when you have not prepared yourself fully. Your preparation should revolve around the following aspects mainly:-
1 Research the organization.
2 Research the job requirements.
3 Prepare technical questions.
4 Prepare informational and behavioural questions.
5 Have a mock interview.