We have all been there. The server pours a splash of wine from the bottle you just ordered. Your job is to taste it and grant permission to pour for the table.
Oh, the pressure! Be honest. You feel it too. I feel it, and I'm supposed to be an expert. But I don't let it get to me anymore. The question should not be whether the wine is off, but whether you like it.
That eliminates the angst over all the many things that can happen to a bottle to waylay the wine. Bad shipping or storage can subject a wine to enough heat to make it taste maderized, or cooked. A leaky cork can introduce oxidation, making a white wine taste like a cut apple that has been left on the counter too long.
Worst of all, a bad cork can taint a wine. A flagrantly corky wine is easy to spot. It smells like wet, moldy newspapers. But many more wines are only slightly affected by a bad cork, and that's not so easy to taste. Sometimes it just dulls the wine, and if you haven't had a good bottle before, you can't know.
And I can't tell you how many times I have wondered if something might be off about the wine, but OK'd it anyway, only to realize 10 minutes later, as the wine opens up the glass, that I blew it. The wine was corky after all, or the oxidation became more apparent.
Yes, someone has to check to make sure it's OK, but it's not fair to make the customer decide, on one quick taste, while everyone at the table is waiting expectantly, whether a wine is acceptable or not. So don't buy into it.
No one expects you to approve your food, to make sure the fish is fresh or the vegetables aren't overcooked, before you eat your dinner. You taste it, think about it, and call back the server if something seems wrong. If the server recommended the dish and you don't like it, you should get a mulligan. It should be the same with wine.
Here's what I do: before I order a wine I have never tasted, I ask the server about it, who should, at the very least, describe it briefly. Then, when I taste the wine, my job is easier. If it tastes as described and nothing at all rings any sort of alarm bells, I nod and let the pouring begin. But if anything about the wine seems not quite right, anything at all, I just say I'm not sure, and ask the server to try it.
In a restaurant with a good wine program, someone should know how the wine should taste and can tell if the bottle is off. In truth, most restaurants aren't that good, but at least you have raised a yellow flag if, 10 minutes later, it's clear that the wine is a no-go.
In any event, if you realize that you don't like the wine, don't be shy about saying so. Unenlightened restaurants may force you to pay for it anyway, but a good restaurateur wants you to be happy. Treat the wine as you would the food. It's a lot easier that way.