I do interviews for my company(also a food outlet). The interview has very strict outlines as to what can be asked and what cannot. These are governed by Government Legislation. eg Religious Orientation, Sexual Preferences, Ageism! But in most cases after a short Maths Test, the interview should be a relaxed informal affair. I would ask things like what are the person Hobbies, Experience they obtained in a working environment, how they have worked in a team at school/college.. What shift Patterns they are able to do. If the person is under 18 there are rules regarding working with Ovens, Knives etc. But in the main it should be as to whether the person wants a job and takes an interest in the company and what his duties/shifts are.