1) Broccoli in the supermodel’s teeth: If a place is beautiful and perfect, except…, let them know. Maybe the stairs leading to the bathroom are dangerously dark, or the organic toilet paper could sand Masa’s bar, or the servers are mispronouncing all the dish names, or they spelled “pintxos” as “pinxtos” on the menu.
Most problems are fixable, and a place would rather know sooner than never see you again. Put another way, this is like telling a friend that his fly’s unzipped or that her underwear is tucked into her dress. Initial embarrassment will quickly turn to gratitude at a problem identified and solved.
2) Bad food preparation or bad ingredients: Failure to correct doneness problems or repeated problems over several courses. Accidents happen, so do patterns. Same goes for off tastes and textures, including aging oysters and gritty greens.
3) Ill-willed or Incompetent Service: See other posts on topic. In short, two questions. I) Was the server advocating for you in the front and back of house? II) Did your server display the professionalism, i.e., hard skills, consonant with the level of dining offered by the restaurant?
4) Food Poisoning (Call!): You awaken with symptoms of food poisoning traceable to your meal. Hop off the pot. Drink some ginger ale. Let the restaurant know by phone as soon as possible. This is not the time to hone your mastery of the epistolary arts. Help others to be spared your experience, and consider this service sufficient reward. That said, chances are good that you’ll be more than adequately compensated by a grateful restaurant.
5) Acknowledge a Wonderful Experience: Slamming a place is dangerously easy. It’s also okay to share the joy. If you can articulate what you liked, you may just get it again, whether it be warm gougères, a Spanish newspaper at the bar, or the greatest waitress to ever come out of Kansas.
Sobremesa: A few more thoughts
Ultimately, you should leave a restaurant feeling happy and restored, thus the word “restaurant.” If you entered unhappy, perhaps you shouldn’t expect a miracle to take place in two hours. If your mood falls during and due to the dining experience, something is probably wrong. After making sure it’s not just you, articulate what was wrong and what could have been done better. If the concerns are concrete and can be turned into suggestions, why not communicate them to the only people capable of offering redress? You can improve your future experience and that of others.