As the first point of contact between a company and the client, a customer service representative must have impeccable communication skills and conflict resolution abilities. Expect your interview to consist of a lot of role-play or "describe a time when..." questions that will test your ability to deal with irate clients, work well under pressure, and always keep a calm and professional composure.
What is your greatest weakness?
Pretty stock question. If you give a stock answer, they don't seem to care. I would try to play around with it though (crack a joke, spin the question into something positive) because that will make you more memorable.
What is your greatest weakness...asking for a job here....