2x interviews (1 with 15 mins reading prep)
Personal statement; unseen poem analysis
Know some relevant terms
Positive thinking
Remember this advice isn't official. There is no guarantee it will reflect your experience because university applications can change between years. Check the official Cambridge and Oxford websites for more accurate information on this year's application format and the required tests.
Also, someone else's experience may not reflect your own. Most interviews are more like conversations than tests and like, any conversation, they are quite interactive.
I had Skype interviews in December, with two interviews in total and two interviewers in each.
The first interview comprised of three random topics I chose to discuss prior to the interview; it was quite informal but challenging. I was also asked to defend my personal statement. The second interview was less informal, with an analysis of an unseen poem given 15 minutes before the interview. It focused on the academic side of things more.
The King's College English reading list helped consolidate my interview preparation. More importantly, have some literary vocabulary in your lexicon to discuss a piece of literature with more technical nuance. I found that thinking of texts I'd like to bring up, prior to the interview, was of great help as well.
I felt positive about my interviews after and I think that safely debunks the whole notion about not getting in if you think it went well. Each interview experience differs, which makes comparisons slightly futile. Enjoy yourself!