Hi
That's great that you got the interview!
I have a had a few casual part time jobs and worked at 2 small cafes - I found it really fun.
I think for any job interview you want to come across as professional and as though you care about the job you are interviewing, so wearing smart clothing would be the best choice unless they specifically tell you otherwise.
In terms of what to do, I would say you want to show that you are friendly and good at customer service if you are working at a café - so smile a lot and make sure you are engaging and friendly to your interviewer. Also show that you know how to be quick on your feet, think of times when you have had to solve problems in a fast paced / crisis situation and that you are a clean and tidy person as you will most likely have to keep the café tidy and clean and tidy up behind the counter/in the kitchen area. Also showing that you are good at working in a team and with other people would be ideal.
Being able to say what skills you have and then giving a specific example of when you were able to show that skill is really important for interviews it shows that you know what will be expected and what you can offer to their company. Preparing to ask at least one question, when they ask you if you have any, is also a great way to show you are eager and engaged. If you are asked what your weaknesses are, say something that you can actually turn into a positive for example don't say "I'm always late" Instead say something that "I always try too hard which means sometimes I can over extend myself and burn out, but I'm learning to get better at doing this by making sure I knowing exactly is expected of me and doing as much as I can to do that but not over doing it" (don't lie though say something that is actually relevant to you!)
You could definitely express you enthusiasm for food and coffee etc.
It also usually really helps to do a practise interview with someone who would know good and relevant questions.
Be confident and you'll do great.
Wishing you all the best
And don't be discouraged if you don't get the job as you aren't going to get every job you apply for sometimes there are just loads of really good candidates etc!
Hope this helps - let me know if you have any more questions!
Jubilee - UoP Rep