Formal:
* Comment vous sentez-vous? (This is the most formal way to ask.)
Informal:
* Comment vas-tu? (This is the most common way to ask friends and family.)
* Comment tu vas? (This is a more casual way to ask.)
* Ça va? (This is a very casual way to ask, similar to "How's it going?")
* Tu te sens comment? (This is a more direct way to ask about someone's feelings.)
To ask about someone's emotional state:
* Comment te sens-tu aujourd'hui? (How are you feeling today?)
* Qu'est-ce qui ne va pas? (What's wrong?)
* Y a-t-il quelque chose qui te tracasse? (Is there something bothering you?)
Remember to adjust your choice of phrase based on the context and your relationship with the person you're talking to.