Author voice is somewhat of a buzz word in the writing/publishing world, wouldn't you agree? I think (read: hope) I have it, but I have a beef with it. It's this amorphous and perplexing idea that authors are told we need to have but aren't told any path to getting it. (And even worse, some are told it's an ON or OFF switch, not a DIMMER, so if you're OFF, give up writing, 'cause it ain't gonna happen.)
I feel that my voice shows up the most in my dialogue. I'm quippy and fairly quick-witted (I like to think) in person. So I like my dialogue exchanges to be the same. I can reproduce this "voice" while my characters are thinking, as well. Of course, I can't be funny all the time, but those are the scenes I just L O V E to write.
So I'm developing a theory to try to put some structure and form to author "voice." Could it be that YOUR voice shows through the scenes you love to write, too? What's so enjoyable about them? Could it be that, on some level, the scene reflects YOU as a person, YOUR quirks, YOUR temperament, something YOU would respond with?