Before going for am interview first ask yourself how prepared are you?
Research about the company that invited you for the interview and ensure you know at least 50% what the company is all about.
If possible ask someone to do a pre interview for you. That can really be of help you to prepare ahead.
Ensure to know how to sell yourself.
Some people don't get the job not because they don't deserve it but because they don't know how to sell themselves in few minutes .
Your appearance also matters alot
Dress smartly and look responsible
Be confident and most of all believe in yourself!