Need opinions on where to eat? They’re easy to find these days, as consumers from around the globe fire off countless raves and pans about every known restaurant, cafe, chili counter, falafel cart and creperie, not to mention post offices and jails. These mash notes and spitballs rain down endlessly not just from traditional review sites like TripAdvisor and Yelp (171 million reviews at last count) and retailers like Amazon, but also from Facebook and Google, those all-purpose giants. Everybody’s a critic, right?

I happen to get paid for criticism, and I would like to criticize that old platitude right out the window: No, everybody is not a critic. What most of you are doing out there, online and in three dimensions, is complaining.

When we complain, we experience something that we don’t like, and we say something about it. A critic doesn’t write about his own dissatisfaction, or doesn’t just do that. A critic has to poke his head out of his turtle shell, look around and gesture, with stubby legs, toward the sources of dissatisfaction. Done perceptively, with analytic thinking and an effort to connect the dots between this experience and others, this can be the beginning of a value system that readers might share, or reject, or at least attempt to understand. Complaining is as easy as breathing. Writing criticism is a real pain. That was a complaint, by the way.

But criticism and complaint are closely related enough for me to know that there’s a lot of complaining going on, and that most of the complaints aren’t having any effect at all. This may not be the point.

People who study complaints divide them into two categories, instrumental and expressive. An instrumental complaint is “directed toward a specific target and intended to bring about a specific outcome,” according to Robin Kowalski, a professor of psychology at Clemson University who has studied the social functions of complaining. Calling a restaurant’s owner the next day to say that you waited an hour for dessert and don’t intend to come back is an instrumental complaint. Texting a friend to say the polar vortex is making your skin peel off is an expressive complaint. We call expressive complaints venting, griping or a number of other names.

It’s important to know which of the two types of complaint is right for you before opening the first can of invective. Venting has its uses. In one study, Kowalski and some colleagues showed that when we are asked to put our feelings of dissatisfaction with somebody into writing, our “positive affect” — good feelings, basically — will rise about 15 minutes later, after an initial downswing. In the same way, if a meal lets you down, taking a pair of pliers and a blowtorch to the restaurant on Yelp might give you a brief lift.

But once the rush of having gotten it off your chest is gone, you’d realize nothing has changed. You’re still out the price of dinner, and you won’t find out whether your grievance has reached the right ears unless somebody at the restaurant responds. Some owners make a point of scouring review sites so they can do just that. Others use the review’s date and details to identify and get in touch with the kvetcher. But there are more direct ways to get your gripe acknowledged.

“If there’s something that’s really bothering you, the ultimate benefits are going to come from targeted complaining,” Kowalski said. “Telling the person or restaurant.”

In other words, have a word with a manager before you leave or soon after. As a side benefit, you’ll be helping the restaurant, too; when somebody is unhappy at the end of a meal, almost any manager or restaurateur wants to know.

“We actually really welcome complaints,” said Melinda Shopsin, a film producer who cooks and waits tables at Shopsin’s, her family’s restaurant on the Lower East Side. This may come as a surprise to anyone who has heard the numerous accounts of customers’ being tossed out of Shopsin’s for any number of arcane infractions. And yet, Shopsin says that when her mother was alive, she would ask what was wrong when she saw an unfinished plate, and then take a bite to see for herself.

If you’re going to make an instrumental complaint, though, you still need to figure out whether the reasons you’re unhappy are subjective or objective. Did Medieval Times undercook the chicken, or do you just not like eating with your hands?

Even if you’re pretty sure the problem is objective, it can be useful to pretend it’s subjective, for the sake of diplomacy. Chef John Tesar recalls a night, soon after he’d opened his Knife steakhouse in Dallas, when he got into an argument with a customer about the weight of a steak — an objective complaint if ever there was one.

“We had a 33-ounce rib-eye for two,” Tesar said. One customer who ordered it wasn’t convinced and began “screaming,” according to Tesar: “‘This steak is too small! This isn’t enough to feed all of us!’” He went to the table, and the hostilities quickly escalated, he said, until “I went into the kitchen, got a scale, grabbed the steak, weighed it in front of her, and said, ‘It’s 36 ounces!’ ” The story ends happily, with the two combatants meeting again at a dinner party some time later and getting along swimmingly. “We both realized how absurd and insecure we were being,” he said.

All this might have been avoided if the complaint had been cast subjectively: “That steak looks smaller than we expected. Are you sure it’s the one we ordered?”

Subjective complaints are still important. If one person doesn’t like the new hot-dog lasagna, it’s an aberration. If 15 people don’t like it, the recipe probably needs work. The chef or owner needs to know this but also needs to hear it in terms that won’t lead to a screaming match. Perhaps you have seen Gordon Ramsay critique another chef’s cooking on television? Don’t do it like that.

In general, the more specific your complaint, the more likely it is to be understood. The worst, most useless and potentially dangerous complaints are broad, sweeping condemnations.

“There is complaining that makes you think about what you’re doing, and there is complaining where everybody thinks they’re entitled to say anything,” said Rita Sodi, chef and owner of the Tuscan restaurant I Sodi in Manhattan. “Saying, ‘This is terrible’ is not complaining. That is being rude. It’s like, ‘You’re ugly.’ It’s telling me that I’m ugly. It’s personal. It’s my food.”