The question ¿Qué tal? usually means "What about
you?". The answer should be positive:
Muy bien – Very good
Genial – Great
If you are not Ok, you can say:
Bien – Good
Más o menos – (lit.) So-so
Regular – So-so / Not well
If you are really bad, you can say:
Mal – Bad
Fatal – Very bad
You can add to Qué tal a name:
¿Qué tal Raúl? – What about Raul?
¿Qué tal tu padre? –
How is your father / How does your father feel?
If you add a common name, the question will refer to a past:
¿Qué tal el concierto? – How was the concert?
¿Qué tal el
examen? – How was your exam? / Did you pass your exam?