Preparation is the key to any interview and lots of people don’t realise this. You wouldn’t go to pitch a new client without any preparation would you? Interviewing for a job is just the same. There are something you need to do, so you won't be caught unaware. making sure the hiring manager knows why you're a good match, researching the company, practice interviewing, what to wear and what to bring to the interview, how to impress during the interview. The fact is this, as tough as an interview is there are ways to prepare yourself physically and mentally for it.
http://career.com.ng/12-things-to-do-when-preparing-for-an-interview

Interviews are one of the hiring tools available to employers, used extensively to judge how appropriate a prospective candidate to fill a role with an organization.

*The Interview provides an opportunity to meet several candidates and screen them to find the ones most suitable for the organization.

*It helps to evaluate a person's skills, capabilities and personality trait.

*Provides tremendous insight into a candidate's confidence level and ability to handle a pressure situation.

* A chance to communicate the Company's policies, beliefs, work culture and expectations from the prospective employee.

* Finally, it helps narrow down, select and hire the best talent to fill the job vacancy. This should ideally be a person who is focused, skilled, confident and excited.

That's why its important for you to get prepared before you go for any interview, so as you can be able to meet your future expectation.

The first thing you must do is to know the necessary criteria an interviewer demand in terms of the quality they need to fill in the vacancy. After that you should write down the quality you posses that are in alignment with what they demand, so that you will be able to share that information with your interviewer when you are asked.

You should research the company you are applying to, to know what they do and how they do it. Do an intensive research on what they need to equip you with sufficient knowledge. This information if well harness will enable you show to your interviewer that you are not here to just work for salary but you have what it takes to do the job professionally. The information will also help you to answer all the questions precisely and give your interviewer that you are vastly knowledgeable in that area.

Take time to practice previous interview questions that you can get your hands on, for it will give you a basic idea of what you will encounter during the interview.
http://career.com.ng/10-common-questions-and-answers-asked-in-an-interview/

Try to get enough rest or go outing with friends to enable you calm all the tensed up nerves before the interview.

Ensure to prepare all the materials that you will need including the dress you will wear on that day, at least two days before the interview day. Always know that looking good is good business so look good, neat and appropriate for the interview because your appearance matter a lot.