How's it going, casually

Qué tal

keh tal — How's it going?

"¡Hola! ¿Qué tal? — Bien, ¿y tú?"
Hi! How's it going? — Good, and you?

More casual and far more common among friends than the textbook "¿Cómo estás?" — use this one and you'll sound like less of a tourist.

"The very first thing I ever taught my first-ever online student, years ago. I still open almost every lesson with it."— Graciela