The process itself is:
1) Phone screen
2) Phone interview
3) In person office visit
4) offer
Passing each phase is based on the experience of each person you speak with, and even after you have finished your formal interview process the opinions of people who you have only momentarily or informally spoken with will be weighed.
Each interview itself is easy though, they ask you basic questions. Behavioral questions like: what is your process for finishing tasks, how do you approach a problem, how have you handled problems in the past, etc. While they do care that you have substantive answers, they care more about whether you can speak and hold an intelligent and professional conversation.