I can share mine. It is basically a telephone call, at the time convinient to the faculty - And you may actually be just waking up from deep sleep! Since I was in a country far away from the institutes I was applying to, there was no personal interview - BUT these are common if you are close to the institute city/state.
There are introductions. Then some standard questions. Why PhD? Are you sure you have some maths experience ? Some quotes - "It is quite quantitative" "Hey , you sure don't wanna do a PhD because you have read some business books. They are trash" (this is response to a statement by me that I liked the book 'The Living Company' by Arie de Geus!). What research have you done ('None' was my answer), Why do you NOW want to do a PhD (I have a LOT of work ex - so this was a difficult one, but I was ok with what I thought about it and said the same thing - that I need to change and go into Academia...). What interests you ?
Normally, a faculty member from the department you apply to (and from your country if there is one) will contact you. It helps to talk in local language perhaps.
KEY : rehearse. Make a list of probable questions on the pattern above. think about what could be asked from your SOP , your CV , your grade sheets, your experience. Prepare answers. Write them down. And lastly, Put the written paper next to telephone.