Soooo I received an acceptance this morning for my third choice. Very strange. Nice to hear something, though!
As for interview pointers, well, just be yourself really! They want to see if you're a good fit, but you also want to see if they're a good fit. Think of questions to ask (i.e. how they conduct thesis supervision) and let the conversation flow. My interview seemed quite long, about 35-40 minutes. We mostly talked about research, so really know your stuff! Of course this will vary from professor to professor, but mine pulled a bunch of questions from my personal statement.
Also, I know I've said this a few times, but my interviewer called half an hour earlier than scheduled. So maybe just be prepared for that!
Sorry, I realize this advice isn't anything groundbreaking, but I really can't stress enough that you should just be yourself.