Dress nicely for the interview (polo shirt, dress slacks, dress shoes) and make sure you are presentable (showered, washed hair - properly combed or brushed, shaved, etc).
Arrive at least 15 minutes early for the interview.
Ask intelligent questions (not "How much vacation do I get?" or "What times are break times?"). Ask questions like "What are the chances for advancement?" (even if you don't plan on making this your "career" - it shows you view this job as more than just a paycheck).
Start the interview off by shaking the interviewer's hand firmly (but don't try to crush it) and making frequent eye contact with the interviewer (but don't stare at them like you're listening to the voices from your Rice Krispies).
Maintain good posture during the interview (and when walking into and out of the store - you never know who might be watching). Don't fold your arms across your chest.
Most importantly, speak like an educated person (but don't put on airs). Refrain from frequent use of slang talk like "you know", "dawg", "like", "dude", etc (this ain't "da hood, dawg") and don't be afraid to blow your own horn if it is merited (but don't be conceited - just state facts like "I saved the company $xx.xx by implementing this procedure", etc).
Hope this helps and good luck!
Remember, if it comes down to you and one other candidate for the job, the first impression you make in the interview could be critical to you getting the job over the other person!
Freight Dogs Anonymous - O.O.T.S.K.
DAMN! This SUCKS! I just had to go to the next higher age bracket in my profile! :-(