I've had two mock interviews and then 1 phone/technical interview. In the mock interviews, we spent about 30 minutes going over general interview questions and technical questions and then 30 minutes on a code challenge. In the phone interview, we spent about 15 minutes on general get-to-know you questions and 30 or so minutes going over a project I worked on and me explaining the code (via screenshare)
For the code challenge portion - just start writing something - pseudocode or anything. Don't just stare at a blank screen. When working on a code challenge, talk out loud about your process. Stay calm.
I think I did well in the get-to-know you type questions and the technical questions for the most part. My first mock interview, the code challenge portion was a disaster and my second one went better.
I will continue to practice more of the cs style technical questions (How does a hash work under the hood) and code challenges.
My first mock intervier was terrible. I was un-prepared and did poorly. My second mock interview, I prepared for it and did much better.