If you are unhappy with your meal in a restaurant, there are different ways to handle the situation.
A lot depends, though, on why you’re unhappy with your meal, and to what extent that is the restaurant’s fault. Let’s say, for instance, that you decided to gamble on something you had never tried, and when you got it you discovered that it’s not something you care for. There’s nothing wrong with the dish; it’s just something that doesn’t fit your tastes, so now you wish you hadn’t ordered it.
In that case, there’s really not much you can do beyond eat what you can of your meal, and treat this as a learning experience where you now know not to order that particular item in the future.
Then there are instances where there isn’t anything blatantly wrong with your meal, but in some lesser way it’s not the quality you were expecting. So maybe your meat is a little under or overcooked, or your pizza uses a thin, disappointingly tasteless tomato sauce, or your soup that should be hot is only lukewarm.
This is not exactly like finding a dead mouse in your spaghetti, but clearly you have at least some grounds to complain.
The thing to do here is to bring the matter to the attention of your server, and politely seek to work out some way to rectify the situation so that the meal will be more satisfactory.
Perhaps your chili can be heated up. Or the limp frozen vegetables can be replaced by some better side item. Or your steak that came out too rare can be put back on the grill for a few minutes.
If you’re nice about it, chances are the restaurant will work with you and try to make things more to your liking.
Then there are the cases where it’s not just that the food is mediocre, or it happens not to be to your tastes, but there’s something objectively, seriously wrong with it, like a health code issue. The aforementioned mouse in your spaghetti, for instance. Or food served on a dish that’s obviously unclean. Or a glass of milk that’s sour.
Here-while you still don’t need to be rude and angry about it-you have a lot more reason to complain and expect satisfaction. You’re not asking the restaurant to bend its rules or do you a favor; you’re bringing to their attention that they’re clearly in the wrong. Depending on how egregious a case it is, it might be enough that they replace what they’ve served you with something better, or it might have gone past that point to where you want nothing to do with their food and expect some other form of compensation.
When things are that bad, and are clearly the restaurant’s fault, stick to your guns. You’re entitled.
In most cases, though, where we aren’t talking about the restaurant having done anything seriously wrong, at most you should mention your dissatisfaction to your server to see if they can perhaps suggest something to make things better, and if that’s not possible, just accept that not every meal you order is going to be great, and at least now you have a little more information to use in the future in deciding what to order, or whether to return to this restaurant at all.