Just be completely honest. Your hopefully future manager wants a hard worker that they can trust so just be as honest as you can. Also do research on starbucks. Being able to refer to your past experiences at your own Starbucks or things you've read show that you've done research and you're actually a fan of starbucks. I got a lot of questions like "what would you do in this situation" "tell me about a time when ___" "why do you want to work at Starbucks" if you're an over thinker like me then going through these questions in your head with different answers is all good but try to keep the interview process relaxed. Mine was like being interviewed by a friend but I'd never even met her before. I hope this helped in some way. If you have any more questions just ask.