how are you

"Come stai?" is the standard way to ask someone how they are doing in an informal context. The mental image is that of a direct, friendly inquiry into the current state of a friend, family member, or someone you are on familiar terms with (using the "tu" form). While "Come stai?" is universally understood, it is strictly for informal settings. In more professional or distant relationships, you would shift to the formal "Come sta?" (using the "Lei" form). Italians often follow this question with "E tu?" (And you?) to keep the conversation flowing.
In conversation
Meeting a friend on the street
Ehi, ciao! Come stai?
Hey, hi! How are you?
Bene, grazie! E tu?
Good, thanks! And you?
A very common, quick greeting between acquaintances.
Checking in via text message
Ciao! È da tanto che non ci sentiamo. Come stai?
Hi! It's been a long time since we spoke. How are you?
Tutto bene, sono solo molto impegnata!
Everything is good, I'm just very busy!
Using the phrase to reconnect after a period of silence.
Examples
Ciao, come stai?
Hi, how are you?
Dimmi, come stai oggi?
Tell me, how are you today?
Non ti vedo da giorni, come stai passando questo periodo?
I haven't seen you for days, how are you spending this time?