Formal:
* O que você faz? (pronounced "oh keh vo-seh fahs?") - This is the most common and literal translation.
* Qual é a sua profissão? (pronounced "kwal eh ah soo-ah pro-fi-ssão?") - This means "What is your profession?"
Informal:
* O que você trabalha? (pronounced "oh keh vo-seh tra-ba-lya?") - This means "What do you work as?"
* Do que você vive? (pronounced "doo keh vo-seh vee-veh?") - This means "What do you live off of?" or "What do you do for a living?"
Other:
* No que você se dedica? (pronounced "noo keh vo-seh seh de-dee-ka?") - This means "What are you dedicated to?"
You can choose the translation that best suits the situation and the person you are talking to.