During my time in 2009, the process was like this:
Initial Interview
Examination
Final Recruiter Interview
Operations Interview
Initial Interview:
Group interview (one interviewer vs many applicants). The basic interview with questions such as "How has been your day so far?", "Tell me something about yourself (that is not written on your resume)", etc.
Tip: Shine out. Start first if you can grab that opportunity. Nothing is more pressuring than having an applicant with a better accent than everyone else in the room including the interviewer talking first.
Examination:
Basic computer question and customer service related scenarios.
Tip: Follow the instructions. If you're called, you're usually out. So do your best to stay on low profile.
Final Recruiter Interview:
Most of the questions in Final Interviews are attitude and behavior related questions mostly. Rarely anyone fails in grammar here, but don't get too comfy. Questions are mostly related in your amenability in working shifting schedule, behavior, motivation etc.
Tip: You are superman. You'll do whatever they need to do. You can start negotiating for better schedule once you're on the floor, but not here.
Operations Interview:
You can fail this interview, and you'll just be endorsed to another campaign. Anyway, still, don't show anything bad. If you're eyeing for a certain account, this is NOT the interview to let the company know that you'd like to be on another account - that should have been done on the Final or Initial interview.