Fry Indicator: French fries are a good indicator. If they are perfect, crisp, clean and hot they have a clean kitchen and expedite their orders well.
View Indicator: View is a great indicator. The better the view the worse the food. Food and service is especially good if the view is blocked by a famous view type place. Fell free to order anything.
Radicle fried indicator: If more than 20% of the menu is filled with fried or “extreme” food all of it sucks.
Buffet indicator: Chinese restaurants without a buffet are usually good.
Deli Case indicator: If there is a deli case close to the front of the building it is a good indicator in quality and freshness. Deli cases are very expensice and usually the rest of the kitchen equipment will be of good qulity and that will resonate throughout the place.
Burger indicator: For a simple food there is much to judge a place by. Is the lettuce crisp? Tomatoes flavorful? Bun warm and fresh? Burger cooked properly? Will they cook it rare?
Chalk Board indicator. A good chalk board is a great sign, Usually…
I agree with lasagna. Come on if you cant make a good one there are serious problems.
Specials Indicator. More than 4 special is a sign of a place that is overcompensating for something. Order off the menu. To much juggling.
Restaurant review indicator: Don’t go to places ranked on the first three in the general category unless they service has max stars. 3-20+ should do a great job. Cuisine specific rating should be okay in the top position but you are better of with 2-5 depending on the size of the city.
Those are a few of my indicators. I have plenty more but decided to stop, especially since I am not addressing the OP’s question exactly.