Sainsbury's Night shift trading assistant

Hi, recently I applied for the sainsbury's night shift trading assistant job and was invited for an interview tomorrow.

This is my first job interview so I am really would like some advice on what to say, where and what kind of clothes to wear and any other expectations they might have for an appropriate candidate.

I have also been invited for a job interview for food production operative at the restaurant Harvester, and if anyone has done this job any advice again would be great.

Also do I have to mention that I have another job interview to the other company?

Hey, bit of general advice here! Dress smart (but don't go over the top, e.g. a nice shirt and smart black jeans), be confident but not cocky, prepare some questions to ask them at the end, have a plan for what they might ask you (e.g. what skills do you have, what could you bring to the company)
I personally wouldn't mention I have another interview, you don't have to but I guess that's purely up to you!
Hope this has helped x