--What do you do?

--I am an engineer.I work for a computer company.What about you?

--I work in a hospital. I am a doctor.

Key points

1.what do you do (for a living)?你是做什么工作的？

I am/She is /You are +a/an+职业

职业：engineer 工程师  doctor  医生

            nurse  护士  reporter  记者

            teacher 教师  chef  厨师

            actor 男演员  actress 女演员

          comedian  喜剧演员

2.work for…为某公司工作

I work for a design/sorftware company

I work for a news station.

3.work in… 在哪里工作

I work in a hospital/theater/school/restaunrant

4.Are you a/an …or (something)?

5.你呢？what/how about you?  you?