NSAA; 3x interviews.
Interview 1: discussion of scenarios; Interview 2: interpreting graphs
Mock interview
Practice papers.
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.
Test taken:
Number of interviews: 3
Time between interviews: 10 mins
Length of interviews: 20 mins
Online interview: No
There was not much discussion of my personal statement. I was mainly given scenarios or graphs to read and discuss/ be asked questions about; often I was given out-of-the-box style questions to answer.
Researched interview techniques and questions, set up
I used practice papers and went over A level content.