Hey Rady,

The best way to prepare yourself for an interview is to practise some of the possible questions that an interviewer might ask you. You can find 10 interview questions and some good replies from some webmembers already on the 'working English' board. Have a look at those and then try to practise with a friend before you go to the interview. This will help make you more confident and relaxed on the interview day itself!
If you don't have any experience, you must emphasise your enthusiasm for doing the new job and indicate that you are a fast learner and would be prepared to spend time to learn the skills required for the job if you are given a chance. It is difficult with no experience, but enthusiasm, excitement and genuine interest in the company you want to work for, go a long way to make up for any skills you don't have at the moment.
Good luck and let us know how you get on!
Have fun,

Paul