Everyone covered your clothing requirements, so what you need to worry about is the interview itself. Spend your evening thinking of answers to the following questions:
-"Tell me about yourself" (brief summary ultimately tying into why you're a good choice for the job)
-Why do you want this role?
-What past experiences have prepared you for this role?
-Think of a time you had to deal with an irate customer. How did you handle the situation?
-What are your key strengths? What is your weakness?
-How do you handle multiple tasks/priorities?
Also, research the company beforehand, they'll probably ask you why you want to work for that company in particular so you should have something in reserve to respond to it. Recruiters love to think you're actually applying for the job because of the company itself, and not just because you need the job.
Also, at the end of the interview they ask if you have any questions for them. Have a few lined up just in case, as it makes you seem interested - nothing about money, and nothing about the company which you could've researched online. Token crap like "How would you describe the responsibilities of the position?" or "How would you describe a typical week/day in this position?" would work.
If you've never been in a formal interview before, you gotta be prepared beforehand unless you really are quick on your feet... you need to prove you're better than the other people they're also interviewing, after all. Good luck!
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I'll see you in Hell! (From Heaven!)