All Right?

So this is a quick post - there is one part of British culture/English I can't adapt to. Rather than saying "What's up?" or "Hello" the Brits often say "All right?" (and yes, they say it as if it were a question). What's the correct response to this? Any American would say "Yea, I'm just fine" or something long those lines, but the correct response is "All right?" - yes, you answer a 'question' with another 'question.' It's quite confusing and I never answer it correctly. I've managed to start to hold my fork in my left hand with my knife in my right but I can't answer a 'question' correctly.

More info here. (Scroll down to "All right?" - continue to read around if you wish.)