[mattgreenrocks]

Word of mouth.

Also, there might be a few heuristics you can use to determine the crud-ness of an employer, but they're not necessarily bulletproof.

Example: if an employer uses Clojure/Haskell currently I'd surmise they're not a complete victim of industry's hype cycle. Whereas if the job ad requested node.js ninjas, not so much. I'd guess it'd be easier to introduce node.js in the former, rather than a functional lang at the latter. But this isn't some amazing inferential leap, really. The subtext of the job post is critical.