Informal:
* क्या चल रहा है? (kyā chal rahā hai?): This literally means "what is happening?" and is the closest informal equivalent of "what's up?".
* क्या हाल है? (kyā hāl hai?): This means "how are you?". It's another common informal greeting.
* क्या खबर है? (kyā khabar hai?): This means "what's the news?". It's similar to "what's up?" but more literal.
Formal:
* आप कैसे हैं? (aap kaise hain?): This means "how are you?" and is used in a formal setting.
* क्या सब ठीक है? (kyā sab ṭhīk hai?): This means "is everything alright?". It's a polite way to inquire about someone's well-being.
Other options:
* सब ठीक है? (sab ṭhīk hai?): This means "everything is fine?". It's a short and simple way to ask about someone's situation.
* क्या हो रहा है? (kyā ho rahā hai?): This literally means "what is happening?". It's a bit more casual than "क्या चल रहा है?".
The best choice for you will depend on your relationship with the person you are talking to and the situation.