You would encounter Personal Interview every time you change job. But PI at MBA admissions has different objectives and those are to test you to know your over all approach, Body language or non verbal skills, Communication skills, presence of mind, reactions and responses from your end on teething questions, your positivity, your mind set, fire in your belly, your quest for achieving goal, your ambitions and how you are planning to achieve them etc.
Since PI being one to one dialogue is so personal that experiences of PI vary from one to the other hence, it is very crucial to understand and stick to basics. It has been found that most of the successful candidates remained cool at personal Interview because they commanded confidence to their armory.
PI is to test you beyond text books and this test is highly circumstantial too but with one mission to select the best at MBA admission.