When can we use the question words "How"and "What"?

Question

At what instance can we use the question words "How" and "what". What is correct? How about you? or "what about you?"

Answer 1

how about u....coz ur asking about the statements in manner w/c something happens or is done w/ him or her.

Answer 2

I've heard either used in casual conversation.
generally How and What cannot be used interchangeably, because How is asking about a process:
"How do you get to your house?"
and What is asking about a thing or event:
"What is that perfume you are wearing?"

If you ask, "How are you doing?" you are asking about the person's health or status, expecting the answer "I'm fine, thanks," but if you ask "What are you doing?" you are asking about their activities and expect "I'm going to school" or something similar; Thus either "How about you?" or "What about you?" are correct, depending upon the intent and context.

Answer 3

'how about you?' means asking about something you feel. While, 'what about you?' means asking about something about him/her.

So, better you choose "How about you?"