"Veldig bra, takk, og du?" is a perfectly legitimate way of answering "Hvordan står det til?". You should be aware however that the 'veldig' suggests you're really doing very well, and not just okay. If that's what you're looking to say, then sure, go ahead and use that. However, the more common, wishy-washy way of answering that question would be "Bare bra, takk, og du?". If you don't like the "og du"-part you can replace that with "og med deg?" or "hva med deg da?"...

Another way is simply adding "da" behind "du". "da" doesn't really mean anything, but it is a word many norwegians add behind a sentence. So simply asking "du da?" or "og med deg da?" also works.