Informal:
* Salut, ça va ? (This is the most common and casual way to say it.)
* Coucou, ça va ? (This is a very informal greeting, often used between friends)
Formal:
* Bonjour, comment allez-vous ? (This is the most polite and formal way to say it.)
* Bonjour, comment allez-vous ? (This is a more formal but still friendly way to say it.)
You can also use:
* Comment vas-tu ? (This is a more informal way to say "how are you" to someone you know well)
* Comment allez-vous ? (This is a more formal way to say "how are you" to someone you don't know well)
The best translation will depend on who you are talking to and the situation.