Here's a post with video: http://www.raysprospects.com/2011/07/matt-moore-tipping-pitches-now-with.html
If you saw the Futures Game or milb.tv, you know Moore's delivery. He brings his hands over his head, then back down before breaking his left hand from his glove and delivering. What I noticed was that on fastballs, he has a tendency to sort of pump the ball into the glove before breaking his hands. It's sort of tough to explain, but I'll call it the glove-pound. It can range in how he does it, from the very subtle to sometimes more obvious (I think it's more obvious when he's trying to pump up the velocity, such as on two strikes).
So anyway, he does that on most of his fastballs. It's not a completely reliable tell -- he didn't do it on every single fastball -- but I don't think he once did the glove-pound and then delivered an off-speed pitch. On his curveball (or slider, whatever you want to call it) and change-up, his left hand doesn't move much if at all.
I'm not sure if a hitter would even be able to see this, but the centerfield angle is good for it, and luckily that's the angle used most often by the Durham TV feed. His stuff is insanely good, and Gwinnett took plenty of awkward swings, clearly fooled on whether a fastball or off-speed pitch comes, a credit to Moore's consistent arm slot and arm speed.