I just did a skype interview with the one of my grad schools. It's definitely important to know who you are interviewing with. I emailed admissions office to find out. Sometimes it's your POI interviewing you it's a random professor in the faculty admissions committee. I was able to do some research on the professor I was interviewing with and that was well received.
I also looked up youtube videos of interview etiquette and most commonly asked questions. Those helped a lot. It's also nice to prepare a list of meaningful questions to show your interests in the program. Review your application essay and CV before the interview. And make sure your sound is good, lighting is good and leave your number with them in case internet connections break.
Finally, after the interview, I suggest sending a thank you email to the professors you met.
Good luck on your interview.