First Round:

We just talked about my past projects, and he was really nice...

Second Round:

General Advice: Be ready to talk about your past projects in depth!

Q: They asked me about the actual details of some of my past projects. I did a microbenchmark on NVDIMM memories at my last coop, so they asked questions about that. 
Q: Then they asked me to explain how the meltdown bug works because I had worked on it in my last coop. They'd never ask you questions like this out of the blue.