How can I best be prepared for an interview?

What do I need to do before an interview?
Give yourself plenty of time to:

research the role and the organization;
think about how well your experience, interests and skills fit the job and the organisation;
research current affairs and trends in your job sector;
find out what the prospective employer is actually looking for;
anticipate questions you might be asked, then prepare answers to these questions;
find out what form the interview will take, e.g. single, panel, group etc.
You should also:

plan the day of the interview, especially your journey with an aim to arrive ten minutes early. Take money in case you need to take a taxi or bus unexpectedly; carry an A-Z street map or put the postcode of the organisation into Google maps on your mobile to prevent getting lost;
decide what you will wear and set it out the night before. Suits and business wear are the best option with comfortable, polished shoes;
get an early night - we all perform better when fully awake.

http://www.prospects.ac.uk/interview_tips_how_to_prepare_for_an_interview.htm

Prepare three examples ahead of time that can be used to answer questions you may be asked during the interview. You can leverage the EAR format to help you stay on track with your responses to questions: Example, Action, Result.

1) Briefly give the example
2) State what action you took
3) Highlight the result of the action and how it addressed the example

Be concise and clear in your responses and always maintain good eye contact.

Hi, great answer above for you. I will add to know and practice some of the common interview questions like:
1) Tell me about yourself 2) What are you strenghts? 3) What are your weaknesses?

http://career-advice.monster.com/job-interview/interview-questions/100-potential-interview-questions/article.aspx

Here is a good link from monster.com with questions and advice.

Good luck!