I'm told by people who know better than I do that I have a natural gift for writing dialog. I've no idea where it came from, but am grateful for it nevertheless. The one issue I had early on was using names too often, but that got picked up by my editor and I've got over it now.
I think you have to listen to people to be able to write great dialog. The cadences and patterns of speach are what you're really trying to capture. But just as important as dialog is silence. Writing silence - now that's a real skill.