When I'm in a foreign city I use these proxies to find a place to eat:

No outside advertising in English: +1 point. Generally, ads in English mean a place is catering to tourists, and thus likely to try and steer me to the non-spicy items, etc.

More than half full with locals: +3 points. This is great as well because then I can just look around and order whatever everyone else is having.

More than half full with tourists: -2 points. I know I talk a lot about signaling, but this is really more for spice, quality and price reasons, not "I want to be different than the crowd" reasons.

The restaurant serves only one item: +3 points. If you serve only one item it has to be at least decent, or you'll go out of business. Furthermore this removes any ambiguity over what to order, and increases the speed with which you're served.

The restaurant's located on the main tourist drag: -3 points: If the rents are high, it'll have to serve everyone, and cater to the lowest common denominator.

The restaurant's in a guidebook: +1 point, although this one's harder to evaluate; I'm not sure what criteria they're using, and their recommendations might be good within each price range. The guidebooks are more likely to recommend places along the main tourist walk.

Unfortunately, saying "Just bring me something good, and spicy" doesn't work too well. When I was in Nainital, I went to two different places a night; it's too cheap not to. I'm looking for suggestions.