I echo what others said. Since it's a video store job and you were referred by a friend you should have a shoe-in unless you completey botch it (aka fart, sneeze on the interviewer, mumble, come in stoned, drunk, or both, come in your pjs, etc.)
Have some answers prepared:
Why should you hire me?
Strengths/weaknesses
Why do you want the job?
How would you handle: a difficult customer, a cash drawer that was short/over, and other job related questions.
Oh and always finish with the questions:
1) Do you have any concerns?
2) What is the next step in this process?
Those 2 things show that you are confident (even if you aren't) and are serious about the job.
Oh and SMILE!
Good luck!
/me gets off the interviewing prep train...ugh, I hated that job
