Your performance in an interview depends, to a significant extent, on how well you prepare. Don't leave this until the last minute. In the days leading up to the interview, focus your research on the:
Employer - you need to show that you understand the business beyond the basics. What job sector does it operate in? What challenges does it face? Who are its competitors? What major projects has it recently completed? What are its culture and values? This kind of knowledge demonstrates a genuine interest.
Role - read the job description again and, if you completed an application form, go over it to refresh your memory of how your skills and qualifications match the role you're applying for. It's vital that you can explain why you want the job, that you understand the role and, even more importantly, why the employer should choose you over other candidates.
Interview panel - try to find out who will be interviewing you. The email inviting you to the interview may include this information. Use LinkedIn and the 'About us' section of the company website to find out more about their professional interests and experience. This may help you to connect with your interviewers and creative a positive impression during the interview.
There are also some practical things to plan. Exactly when and where is the interview taking place? Have you planned your journey and checked the timetables for any public transport you need to take? What will you eat before the interview?