One of the keys to a successful interview is to approach the interviewer from the perspective of the interviewer. As they speak to you, interviewers will ask themselves questions like “Do I like this person,” “Is he/she a good fit for this school,” and “Can I see myself teaching him/her as a medical school, consulting with him/her as a colleague, or referring family members to him/her as a patient?” Stress interviews are the rare exception, not the rule. It is much more likely that your interview will be relaxed and conversational. The idea is not to worry but to prepare.
Here are some helpful links and online resources.