You need to contact a professor and/or committee to look for open positions. Interview depends on the professor and can vary a lot. Mine went pretty smoothly. I just showed up in semi-formal wear and did the interview.
I applied through university. I interviewed at UC Davis
Interview
Interviewed by the professor and the chair of the department. Asked about related course works and thoughts about the course materials. Not really hard, but try to show the communication skills and good personality.
