Formal:
* Onde está você? (pronounced "ondeh ehshtah vohseh?") - This is the most common and formal way to ask.
* Onde se encontra? (pronounced "ondeh seh enkown-tra?") - This is a more formal and literary way to ask.
Informal:
* Onde você está? (pronounced "ondeh vohseh ehshtah?") - This is the most common informal way to ask.
* Cadê você? (pronounced "kah-deh vohseh?") - This is a very informal and colloquial way to ask, similar to "where's at" in English.
When asking for location:
* Onde você mora? (pronounced "ondeh vohseh moh-rah?") - "Where do you live?"
* Onde você trabalha? (pronounced "ondeh vohseh trah-bah-lyah?") - "Where do you work?"
* Onde você está agora? (pronounced "ondeh vohseh ehshtah ah-goh-rah?") - "Where are you now?"
The best choice depends on who you're speaking to and the context of the conversation.