This tip from Least Heat Moon's, "Blue Highways to America," has proven accurate as a law of nature in the 20 years since I read the book.

Moon says the quality of a mom-n-pop eatery can be judged by the number of calanders behind the registers. Your M&P, unlike chain resturants, exists in the network of favors given and taken among local businesses. The more calanders, the more the joint depends on repeat, local customers. Hence the better the eats.

This has served me well, not only in the blue higheays of the USA, but in other lands as well.