Going into an interview there are some things you can control and others you cannot. You cannot control how much or what type of experience you have. You cannot control your prior educational background or work history. Presumably, you have enough of what an employer is looking for to spark some interest, which is why you are getting the chance to interview. At this point, you play a major part in determining your own fate.
In preparing for an interview, give some thought to what you are going to wear, make sure you read up on the employer/company and review any other job-related information. These are all things you can control prior to the actual interview, but do not discount how much your attitude during the interview comes into play. In particular, you want to appear confident (not cocky) and show some genuine excitement about the opportunity. First, if you cannot show confidence in your own abilities then do not expect the employer be confident that you are the right fit for the job. Second, it is okay to show some excitement about the prospect of getting the job. Everyone wants to feel wanted and if the employer can see that you are genuinely excited about the job and working with the firm/company in general, it can really help your cause. Likewise, if you appear indifferent or too reserved it can leave a lasting negative impression.
Our experience has shown that attitude/personality has more to do with whether an interviewee moves forward than their actual experience. This is encouraging to know when you are up against others with more on point experience but can still blow it with a less than stellar attitude. The key for you is to capitalize on those things you can control and just remember that attitude is everything.