Here's one to look for: a solid top. You want that a bit more than solid sides. And you look for that by looking at the soundhole. If the top is laminate, you'll see layers in the edge of the soundhole, but if the wood's solid, it will look solid.
Action is something that will kill you if you want to get beyond the cowboy chords. You want it somewhat high so the strings vibrate clearly and don't hit the frets, but if it seems like you can stick a deck of playing cards between the strings and the fretboard, that's way high.
There's a thing called a zero fret, sitting right after the nut. I've heard of some high-end makers using them, but by and large, I see it as a cost-saving measure by low-end makers, and I don't think I've seen one in some time. In your price range, it's more an indicator of low quality than not.