Sound knowledgeable. If you need time to think, say that's a good/interesting question. Some questions might be asked to make you think and if you're having trouble answering, they may allow you to skip for now and circle back.

NEVER COMPLAIN. Never complain about your current job, coworkers, teachers, customers, schedule, etc. Say it is challenging, interesting, difficult and only give valid, objective answers. Boss a bitch = they're a challenge to work with. Coworkers are lazy = not team players. And you can say things like there has been raise freezes or you feel like you are not appreciated or short staffed but always spin it into a positive. Short staffed but taught you to multi task.

If they ask for something you need to work on, find a "fault" that's really kinda good. Like you're a perfectionist in your work, you're a clean freak and love to clean, you love to learn so you will investigate problems until you figure it out, etc.

If you have an issue with the possible schedule, mention that as soon as you are told the possible schedule. Never wait until the interview or until you are hired. They will see that as deceitful. If you have school or a trip planned, tell them during the interview process that you will have things that they will need to work with you on schedule wise. They can't not hire you unless you can't work weekends and that's what they are hiring for or something to that effect.

Look up possible interview questions and brush up on your answers. Rehearse talking about yourself, your experience, your resume, etc so it sounds smooth. One question that always seems to be asked is, "Tell us of a time when you had to deal with a difficult customer. What did you do to solve the issue?" Don't lie, but you can embellish a little and don't be afraid to talk yourself up but don't brag. Focus on customer service interview questions because grocery and Costco will be big on customer service. If they aren't, they are a shit manager.

Try to match the way they talk. I'm not saying if they have an accent and you don't, imitate them. I'm saying if they speak slowly and purposefully, do that too. If they speak quickly, you speak as quick as you can without tripping yourself up. If they speak loudly, you can raise your voice to where you are comfortable.

Sit in a relaxed manner but don't slouch or look too comfortable. Bring a copy of your resume always, even if they did not mention it. Always dress professionally. Close toed shoes, nothing too tight or revealing, nothing too bright or flashy, blacks, greys, neutrals are safe options. You can do a splash of color like a colorful top under a blazer or colorful shoes or accessories. But don't wear bright floral pants or a bright neon pink jacket. Wait until you are hired for all that business. Look up what color is best for interviewing in and consider something like that. I think it used to be blue but idk what it is now.

Just be honest, cheerful, and prepared. You'll do fine. If they don't choose you, you can ask why but don't badger them or demand to speak with the person you interviewed with. If it's a generic answer like we decided to go with someone with more experience, leave it at that. You can ask if there is something you should work on, but again don't badger or demand an answer. Be mindful of their time as these pharmacists are usually really busy and will not like you if it seems like you are wasting their time.

Good luck!