moxfyre

I look for rideability, mostly. If all the parts are crappy and not easily upgradeable, it's not worth it.

My quick "quality check" involves looking for cranks with bolts rather than rivets (instant good sign), CroMoly stickers (better than cheap carbon steel frame), Allen bolts rather than hex bolts, etc. Another small thing for old ten-speeds: the cheap ones use stem/seat/brake clamps that aren't threaded, so the bolts have nuts on the ends. On the nicer models the clamps are threaded so no ugly nuts sticking out.