* Quid agis? This is a common and informal way to ask "How are you doing?" or "What are you doing?" It's suitable for friends and equals.
* Quid agitis? This is the plural form of "Quid agis?", used when addressing more than one person.
* Valete? This literally translates to "Are you well?" or "Farewell (in the sense of 'I hope you are well')" and is a more formal and polite way to inquire about someone's well-being. The plural is also *Valete*.
* Quomodo vales? This translates more literally to "How are you well?" and is a more formal way of asking. The plural is *Quomodo valetis?*
The best option depends on the context and your relationship with the person you're addressing. `Quid agis?` is generally the safest and most commonly used informal option.