Informal:
* શું ચાલે છે? (shu chale che?) - This is the most common and casual way to say "what's up?"
* કેવું છે? (kevu che?) - This literally means "how are you?" but can be used as a casual greeting similar to "what's up?"
Formal:
* શું ખબર છે? (shu khabar che?) - This is a more formal way to ask "what's up?" and translates to "what's the news?"
* કેવું થાય છે? (kevu thay che?) - This is another formal way to ask "how are you?" and can be used as a greeting similar to "what's up?"
Other options:
* તમને કેવું છે? (tamne kevu che?) - This is a polite way to ask "how are you?" and can be used in a formal or informal setting.
The best option to use will depend on the situation and your relationship with the person you are speaking to.