You can never really know what people will ask you on these interviews. At the very least know yourself and be ready to answer, the common questions of why PA, why not other jobs, what makes you a good candidate, tell me about yourself, etc are ones I hear a lot. You might stumble over some medical ethical questions, but that's just the nature of the question. As @PrePAlife said it's easier to be yourself than somebody else. Just be personable, exhibit good soft skills, be confident, and give it your best.