Wellllllllll, maybe. Hot bread is a great treat, but ideally a good artisan loaf or baguette should be allowed to cool on a rack for the proper amount of time. It’s super important for the quality of the crumb and less (but still) important for the crust. A really good baguette can easily last a day, unrefrigerated, with no loss of flavor, just so long as it isn’t sliced until just before it’s served.
Anyway, I always order ropa vieja at a latin restaurant and Wonton Soup at a chinese place.
I judge Chinese places by their ma po tofu (spicy tofu cubes) and scallion pancakes. Some places don’t carry either.
I’m not strictly vegetarian but it’s nice if a place has a few options.
I would have to disagree. There is a very good Mexican restaurant near me that doesn’t have menudo (I won’t eat it either!) on the menu, simply because there’s no demand for it. This is straight from the owner (was curious and asked). As an aside, this place actually cooks their own beans. No difficult task I know, but I imagine not too many places do! Nothing like fresh cooked beans!
Someone mentioned upthread about rare hamburgers. Well, cooks are advised to avoid this for health issues. The first time a customer gets sick eating a rare burger could very well mean closure for a restaurant. Please remember that the next time you ask! 
If it’s a place that specializes in thick burgers then, sorry, I’m going to disqualify it if it doesn’t serve them rare or medium rare. I’ll cut them slack for thin patties/fast-food-style burgers which are almost impossible to cook to lower levels of doneness, but for those thick patties? If I can’t get it at as rare as medium rare, there’s just no point in that burger.
Thankfully, none of the burger joints here are like that.
In the neighborhood where I work, there are many, many Mexican restaurants, and my colleagues and I have tried them ALL (repeatedly). I judge a Mexican restaurant by its refried beans. Grounds for rejection are: no taste, wrong texture, too smoky, too watery, noticeably greasy, too salty, or just plain “yuck.” There are a couple of restaurants that make SUPERB refried beans: perfect texture without too much moisture, very tasty without relying on bacon or the like. Something simple like this (or like a scrambled egg, for example) takes real skill to do right.
Diner: I love chicken-fried steak and will give it a try. If they fuck up the gravy or the meat is all gristly, I’m done with the place. If they don’t have that, but have biscuits and gravy, I’ll try that, even though I know it won’t measure up to mine. Again, if the cook can’t make gravy (or biscuits, for that matter), everything else is suspect. Chicken pot pie is a good litmus also; a flavorless gruel with a couple of tiny pieces of chicken in it is not going to win my return business. Sandwiches: those thick slices of bread are a deal breaker, regardless of how rhapsodic your menu is about it.
Italian: Carbonara used to be my litmus test, but pretty much anything that takes a sauce will do. If the dish is drowning in the stuff, then it’s Amer-italian: not necessarily bad, but not what I’m looking for. Lasagna is a good indicator, but a bad lasagna is such a disappointment that I hate to take a chance.
Burger joint: If the burger isn’t freshly made (not frozen), it’s a non-starter. If the bun is stale, I won’t be back. I can deal with frozen fries, but they have to be fresh out of the fryer; if they’ve been sitting under a heat lamp, that tells me the kitchen is lazy and disorganized.
Southwest: carne adovada. If the meat is fatty, that’s it for me.
Restaurants that hide their food behind incomprehensible descriptions do not get my business. “Canardons suissant with pecarillos of dijoned camareens - $32” makes me cranky. If I have to ask what the hell it is, then I feel like I’m being patronized by the chef.
It’s not an exclusive sign, but it still works. Our second-favorite spot in town doesn’t serve it either. No demand. But if I’m in a new town and have no idea which place is the best, I’m going to look for the menudo sign. Just like when I hunt down a BBQ joint. I’ll ask around. One of the first questions I ask is “Do they have plates?” If the answer is no, I head there fast.
For a Mexican or Central American place, a simple taco de lengua or pupusa revuelta or tamale can tell you how good they are.