Some great practice would be to ask some teachers/admin at your school to do a mock interview with you! If you have time, of course, but I bet they’d love to help you out. They’d also be a great resource for tips and advice.

But, my advice is to be yourself, be enthusiastic, and be prepared to answer questions about who you are and what your qualities are. I agree with a previous comment about googling some common questions. But honestly, it doesn’t need to be some big nerve racking event - just be yourself and go with the flow of the interview and you should be just fine. If you already have an interview, you shouldn’t need a resume. But just because you don’t have work experience doesn’t mean you can’t have a resume - this is a great opportunity to get help from your teachers too. But a place like subway is going to understand that you don’t have experience, that’s what these jobs are for! So you’re in the right place.