The interview advice here is excellent. Ask questions - in the current climate they're hunting you, not the other way around.

Additionally, start networking now. Get to know ace developers in your area, and you will start hearing about top-level development shops. Go to meetups and other events where strong developers are likely to gather (or really, developers who give a shit about proper engineering) and meet people there.

It's next to impossible to know, walking into an office building, whether the company is a fucked up joke or good at what it does - people will tell you.