A recruiter reached out to me about a project manager opportunity. There were three rounds of interviews: (1) a HR screen, and then (2) and (3) two rounds of interviews with people I'd potentially be working with. The second round of interviews was rather cursory--the interviewer asked a few questions, but it wasn't particularly in depth. The third (last) round of interviews was far more in depth. It's cliche, but make sure you can talk knowledgeably about everything on your resume.
The company was a little too eager to schedule interviews--the tendency was to try to schedule interviews immediately for the next business day. I appreciate the lack of red tape, but it's not always easy to drop everything and block off time for an interview.
I never had a lot of clarity about what position I was interviewing for. The title/job description kept changing (possibly because the position was filled?). I had multiple interviews where I thought I was interviewing for one position and it turned out that I was interviewing for a completely different one. It's difficult to prepare when you don't know what position you're interviewing for.